OpenCloudOS-Kernel/mm/mincore.c

305 lines
7.6 KiB
C
Raw Normal View History

License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 22:07:57 +08:00
// SPDX-License-Identifier: GPL-2.0
/*
* linux/mm/mincore.c
*
* Copyright (C) 1994-2006 Linus Torvalds
*/
/*
* The mincore() system call.
*/
#include <linux/pagemap.h>
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h percpu.h is included by sched.h and module.h and thus ends up being included when building most .c files. percpu.h includes slab.h which in turn includes gfp.h making everything defined by the two files universally available and complicating inclusion dependencies. percpu.h -> slab.h dependency is about to be removed. Prepare for this change by updating users of gfp and slab facilities include those headers directly instead of assuming availability. As this conversion needs to touch large number of source files, the following script is used as the basis of conversion. http://userweb.kernel.org/~tj/misc/slabh-sweep.py The script does the followings. * Scan files for gfp and slab usages and update includes such that only the necessary includes are there. ie. if only gfp is used, gfp.h, if slab is used, slab.h. * When the script inserts a new include, it looks at the include blocks and try to put the new include such that its order conforms to its surrounding. It's put in the include block which contains core kernel includes, in the same order that the rest are ordered - alphabetical, Christmas tree, rev-Xmas-tree or at the end if there doesn't seem to be any matching order. * If the script can't find a place to put a new include (mostly because the file doesn't have fitting include block), it prints out an error message indicating which .h file needs to be added to the file. The conversion was done in the following steps. 1. The initial automatic conversion of all .c files updated slightly over 4000 files, deleting around 700 includes and adding ~480 gfp.h and ~3000 slab.h inclusions. The script emitted errors for ~400 files. 2. Each error was manually checked. Some didn't need the inclusion, some needed manual addition while adding it to implementation .h or embedding .c file was more appropriate for others. This step added inclusions to around 150 files. 3. The script was run again and the output was compared to the edits from #2 to make sure no file was left behind. 4. Several build tests were done and a couple of problems were fixed. e.g. lib/decompress_*.c used malloc/free() wrappers around slab APIs requiring slab.h to be added manually. 5. The script was run on all .h files but without automatically editing them as sprinkling gfp.h and slab.h inclusions around .h files could easily lead to inclusion dependency hell. Most gfp.h inclusion directives were ignored as stuff from gfp.h was usually wildly available and often used in preprocessor macros. Each slab.h inclusion directive was examined and added manually as necessary. 6. percpu.h was updated not to include slab.h. 7. Build test were done on the following configurations and failures were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my distributed build env didn't work with gcov compiles) and a few more options had to be turned off depending on archs to make things build (like ipr on powerpc/64 which failed due to missing writeq). * x86 and x86_64 UP and SMP allmodconfig and a custom test config. * powerpc and powerpc64 SMP allmodconfig * sparc and sparc64 SMP allmodconfig * ia64 SMP allmodconfig * s390 SMP allmodconfig * alpha SMP allmodconfig * um on x86_64 SMP allmodconfig 8. percpu.h modifications were reverted so that it could be applied as a separate patch and serve as bisection point. Given the fact that I had only a couple of failures from tests on step 6, I'm fairly confident about the coverage of this conversion patch. If there is a breakage, it's likely to be something in one of the arch headers which should be easily discoverable easily on most builds of the specific arch. Signed-off-by: Tejun Heo <tj@kernel.org> Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 16:04:11 +08:00
#include <linux/gfp.h>
#include <linux/pagewalk.h>
#include <linux/mman.h>
#include <linux/syscalls.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/shmem_fs.h>
mm: hugetlb: fix hugepage memory leak in mincore() Most callers of pmd_none_or_clear_bad() check whether the target page is in a hugepage or not, but mincore() and walk_page_range() do not check it. So if we use mincore() on a hugepage on x86 machine, the hugepage memory is leaked as shown below. This patch fixes it by extending mincore() system call to support hugepages. Details ======= My test program (leak_mincore) works as follows: - creat() and mmap() a file on hugetlbfs (file size is 200MB == 100 hugepages,) - read()/write() something on it, - call mincore() for first ten pages and printf() the values of *vec - munmap() and unlink() the file on hugetlbfs Without my patch ---------------- $ cat /proc/meminfo| grep "HugePage" HugePages_Total: 1000 HugePages_Free: 1000 HugePages_Rsvd: 0 HugePages_Surp: 0 $ ./leak_mincore vec[0] 0 vec[1] 0 vec[2] 0 vec[3] 0 vec[4] 0 vec[5] 0 vec[6] 0 vec[7] 0 vec[8] 0 vec[9] 0 $ cat /proc/meminfo |grep "HugePage" HugePages_Total: 1000 HugePages_Free: 999 HugePages_Rsvd: 0 HugePages_Surp: 0 $ ls /hugetlbfs/ $ Return values in *vec from mincore() are set to 0, while the hugepage should be in memory, and 1 hugepage is still accounted as used while there is no file on hugetlbfs. With my patch ------------- $ cat /proc/meminfo| grep "HugePage" HugePages_Total: 1000 HugePages_Free: 1000 HugePages_Rsvd: 0 HugePages_Surp: 0 $ ./leak_mincore vec[0] 1 vec[1] 1 vec[2] 1 vec[3] 1 vec[4] 1 vec[5] 1 vec[6] 1 vec[7] 1 vec[8] 1 vec[9] 1 $ cat /proc/meminfo |grep "HugePage" HugePages_Total: 1000 HugePages_Free: 1000 HugePages_Rsvd: 0 HugePages_Surp: 0 $ ls /hugetlbfs/ $ Return value in *vec set to 1 and no memory leaks. [akpm@linux-foundation.org: cleanup] [akpm@linux-foundation.org: build fix] Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Andy Whitcroft <apw@canonical.com> Cc: David Rientjes <rientjes@google.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-12-15 09:59:58 +08:00
#include <linux/hugetlb.h>
#include <linux/uaccess.h>
#include <asm/pgtable.h>
static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
unsigned long end, struct mm_walk *walk)
{
#ifdef CONFIG_HUGETLB_PAGE
unsigned char present;
unsigned char *vec = walk->private;
/*
* Hugepages under user process are always in RAM and never
* swapped out, but theoretically it needs to be checked.
*/
present = pte && !huge_pte_none(huge_ptep_get(pte));
for (; addr != end; vec++, addr += PAGE_SIZE)
*vec = present;
walk->private = vec;
#else
BUG();
#endif
return 0;
}
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
/*
* Later we can get more picky about what "in core" means precisely.
* For now, simply check to see if the page is in the page cache,
* and is up to date; i.e. that no page-in operation would be required
* at this time if an application were to map and access this page.
*/
static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
{
unsigned char present = 0;
struct page *page;
/*
* When tmpfs swaps out a page from a file, any process mapping that
* file will not get a swp_entry_t in its pte, but rather it is like
* any other file mapping (ie. marked !present and faulted in with
* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
*/
#ifdef CONFIG_SWAP
if (shmem_mapping(mapping)) {
page = find_get_entry(mapping, pgoff);
/*
* shmem/tmpfs may return swap: account for swapcache
* page too.
*/
if (xa_is_value(page)) {
swp_entry_t swp = radix_to_swp_entry(page);
mm/mincore.c: fix race between swapoff and mincore Via commit 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks"), after swapoff, the address_space associated with the swap device will be freed. So swap_address_space() users which touch the address_space need some kind of mechanism to prevent the address_space from being freed during accessing. When mincore processes an unmapped range for swapped shmem pages, it doesn't hold the lock to prevent swap device from being swapped off. So the following race is possible: CPU1 CPU2 do_mincore() swapoff() walk_page_range() mincore_unmapped_range() __mincore_unmapped_range mincore_page as = swap_address_space() ... exit_swap_address_space() ... kvfree(spaces) find_get_page(as) The address space may be accessed after being freed. To fix the race, get_swap_device()/put_swap_device() is used to enclose find_get_page() to check whether the swap entry is valid and prevent the swap device from being swapoff during accessing. Link: http://lkml.kernel.org/r/20190611020510.28251-1-ying.huang@intel.com Fixes: 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks") Signed-off-by: "Huang, Ying" <ying.huang@intel.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Hugh Dickins <hughd@google.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Yang Shi <yang.shi@linux.alibaba.com> Cc: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Daniel Jordan <daniel.m.jordan@oracle.com> Cc: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-12 11:55:44 +08:00
struct swap_info_struct *si;
/* Prevent swap device to being swapoff under us */
si = get_swap_device(swp);
if (si) {
page = find_get_page(swap_address_space(swp),
swp_offset(swp));
put_swap_device(si);
} else
page = NULL;
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
}
} else
page = find_get_page(mapping, pgoff);
#else
page = find_get_page(mapping, pgoff);
#endif
if (page) {
present = PageUptodate(page);
put_page(page);
}
return present;
}
static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
struct vm_area_struct *vma, unsigned char *vec)
{
Change mincore() to count "mapped" pages rather than "cached" pages The semantics of what "in core" means for the mincore() system call are somewhat unclear, but Linux has always (since 2.3.52, which is when mincore() was initially done) treated it as "page is available in page cache" rather than "page is mapped in the mapping". The problem with that traditional semantic is that it exposes a lot of system cache state that it really probably shouldn't, and that users shouldn't really even care about. So let's try to avoid that information leak by simply changing the semantics to be that mincore() counts actual mapped pages, not pages that might be cheaply mapped if they were faulted (note the "might be" part of the old semantics: being in the cache doesn't actually guarantee that you can access them without IO anyway, since things like network filesystems may have to revalidate the cache before use). In many ways the old semantics were somewhat insane even aside from the information leak issue. From the very beginning (and that beginning is a long time ago: 2.3.52 was released in March 2000, I think), the code had a comment saying Later we can get more picky about what "in core" means precisely. and this is that "later". Admittedly it is much later than is really comfortable. NOTE! This is a real semantic change, and it is for example known to change the output of "fincore", since that program literally does a mmmap without populating it, and then doing "mincore()" on that mapping that doesn't actually have any pages in it. I'm hoping that nobody actually has any workflow that cares, and the info leak is real. We may have to do something different if it turns out that people have valid reasons to want the old semantics, and if we can limit the information leak sanely. Cc: Kevin Easton <kevin@guarana.org> Cc: Jiri Kosina <jikos@kernel.org> Cc: Masatake YAMATO <yamato@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-06 09:50:59 +08:00
unsigned long nr = (end - addr) >> PAGE_SHIFT;
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
int i;
Change mincore() to count "mapped" pages rather than "cached" pages The semantics of what "in core" means for the mincore() system call are somewhat unclear, but Linux has always (since 2.3.52, which is when mincore() was initially done) treated it as "page is available in page cache" rather than "page is mapped in the mapping". The problem with that traditional semantic is that it exposes a lot of system cache state that it really probably shouldn't, and that users shouldn't really even care about. So let's try to avoid that information leak by simply changing the semantics to be that mincore() counts actual mapped pages, not pages that might be cheaply mapped if they were faulted (note the "might be" part of the old semantics: being in the cache doesn't actually guarantee that you can access them without IO anyway, since things like network filesystems may have to revalidate the cache before use). In many ways the old semantics were somewhat insane even aside from the information leak issue. From the very beginning (and that beginning is a long time ago: 2.3.52 was released in March 2000, I think), the code had a comment saying Later we can get more picky about what "in core" means precisely. and this is that "later". Admittedly it is much later than is really comfortable. NOTE! This is a real semantic change, and it is for example known to change the output of "fincore", since that program literally does a mmmap without populating it, and then doing "mincore()" on that mapping that doesn't actually have any pages in it. I'm hoping that nobody actually has any workflow that cares, and the info leak is real. We may have to do something different if it turns out that people have valid reasons to want the old semantics, and if we can limit the information leak sanely. Cc: Kevin Easton <kevin@guarana.org> Cc: Jiri Kosina <jikos@kernel.org> Cc: Masatake YAMATO <yamato@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-06 09:50:59 +08:00
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
if (vma->vm_file) {
pgoff_t pgoff;
pgoff = linear_page_index(vma, addr);
for (i = 0; i < nr; i++, pgoff++)
vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
} else {
for (i = 0; i < nr; i++)
vec[i] = 0;
}
return nr;
}
static int mincore_unmapped_range(unsigned long addr, unsigned long end,
mm: pagewalk: add 'depth' parameter to pte_hole The pte_hole() callback is called at multiple levels of the page tables. Code dumping the kernel page tables needs to know what at what depth the missing entry is. Add this is an extra parameter to pte_hole(). When the depth isn't know (e.g. processing a vma) then -1 is passed. The depth that is reported is the actual level where the entry is missing (ignoring any folding that is in place), i.e. any levels where PTRS_PER_P?D is set to 1 are ignored. Note that depth starts at 0 for a PGD so that PUD/PMD/PTE retain their natural numbers as levels 2/3/4. Link: http://lkml.kernel.org/r/20191218162402.45610-16-steven.price@arm.com Signed-off-by: Steven Price <steven.price@arm.com> Tested-by: Zong Li <zong.li@sifive.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Hogan <jhogan@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Liang, Kan" <kan.liang@linux.intel.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Burton <paul.burton@mips.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-02-04 09:36:03 +08:00
__always_unused int depth,
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
struct mm_walk *walk)
{
walk->private += __mincore_unmapped_range(addr, end,
walk->vma, walk->private);
return 0;
}
static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
spinlock_t *ptl;
struct vm_area_struct *vma = walk->vma;
pte_t *ptep;
unsigned char *vec = walk->private;
int nr = (end - addr) >> PAGE_SHIFT;
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
memset(vec, 1, nr);
spin_unlock(ptl);
goto out;
}
if (pmd_trans_unstable(pmd)) {
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
__mincore_unmapped_range(addr, end, vma, vec);
goto out;
}
ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
for (; addr != end; ptep++, addr += PAGE_SIZE) {
pte_t pte = *ptep;
if (pte_none(pte))
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
__mincore_unmapped_range(addr, addr + PAGE_SIZE,
vma, vec);
else if (pte_present(pte))
*vec = 1;
else { /* pte is a swap entry */
swp_entry_t entry = pte_to_swp_entry(pte);
Revert "Change mincore() to count "mapped" pages rather than "cached" pages" This reverts commit 574823bfab82d9d8fa47f422778043fbb4b4f50e. It turns out that my hope that we could just remove the code that exposes the cache residency status from mincore() was too optimistic. There are various random users that want it, and one example would be the Netflix database cluster maintenance. To quote Josh Snyder: "For Netflix, losing accurate information from the mincore syscall would lengthen database cluster maintenance operations from days to months. We rely on cross-process mincore to migrate the contents of a page cache from machine to machine, and across reboots. To do this, I wrote and maintain happycache [1], a page cache dumper/loader tool. It is quite similar in architecture to pgfincore, except that it is agnostic to workload. The gist of happycache's operation is "produce a dump of residence status for each page, do some operation, then reload exactly the same pages which were present before." happycache is entirely dependent on accurate reporting of the in-core status of file-backed pages, as accessed by another process. We primarily use happycache with Cassandra, which (like Postgres + pgfincore) relies heavily on OS page cache to reduce disk accesses. Because our workloads never experience a cold page cache, we are able to provision hardware for a peak utilization level that is far lower than the hypothetical "every query is a cache miss" peak. A database warmed by happycache can be ready for service in seconds (bounded only by the performance of the drives and the I/O subsystem), with no period of in-service degradation. By contrast, putting a database in service without a page cache entails a potentially unbounded period of degradation (at Netflix, the time to populate a single node's cache via natural cache misses varies by workload from hours to weeks). If a single node upgrade were to take weeks, then upgrading an entire cluster would take months. Since we want to apply security upgrades (and other things) on a somewhat tighter schedule, we would have to develop more complex solutions to provide the same functionality already provided by mincore. At the bottom line, happycache is designed to benignly exploit the same information leak documented in the paper [2]. I think it makes perfect sense to remove cross-process mincore functionality from unprivileged users, but not to remove it entirely" We do have an alternate approach that limits the cache residency reporting only to processes that have write permissions to the file, so we can fix the original information leak issue that way. It involves _adding_ code rather than removing it, which is sad, but hey, at least we haven't found any users that would find the restrictions unacceptable. So revert the optimistic first approach to make room for that alternate fix instead. Reported-by: Josh Snyder <joshs@netflix.com> Cc: Jiri Kosina <jikos@kernel.org> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-24 04:04:37 +08:00
if (non_swap_entry(entry)) {
/*
* migration or hwpoison entries are always
* uptodate
*/
*vec = 1;
} else {
#ifdef CONFIG_SWAP
*vec = mincore_page(swap_address_space(entry),
swp_offset(entry));
#else
WARN_ON(1);
*vec = 1;
#endif
}
}
vec++;
}
pte_unmap_unlock(ptep - 1, ptl);
out:
walk->private += nr;
cond_resched();
return 0;
}
mm/mincore.c: make mincore() more conservative The semantics of what mincore() considers to be resident is not completely clear, but Linux has always (since 2.3.52, which is when mincore() was initially done) treated it as "page is available in page cache". That's potentially a problem, as that [in]directly exposes meta-information about pagecache / memory mapping state even about memory not strictly belonging to the process executing the syscall, opening possibilities for sidechannel attacks. Change the semantics of mincore() so that it only reveals pagecache information for non-anonymous mappings that belog to files that the calling process could (if it tried to) successfully open for writing; otherwise we'd be including shared non-exclusive mappings, which - is the sidechannel - is not the usecase for mincore(), as that's primarily used for data, not (shared) text [jkosina@suse.cz: v2] Link: http://lkml.kernel.org/r/20190312141708.6652-2-vbabka@suse.cz [mhocko@suse.com: restructure can_do_mincore() conditions] Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1903062342020.19912@cbobk.fhfr.pm Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Josh Snyder <joshs@netflix.com> Acked-by: Michal Hocko <mhocko@suse.com> Originally-by: Linus Torvalds <torvalds@linux-foundation.org> Originally-by: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-05-15 06:41:38 +08:00
static inline bool can_do_mincore(struct vm_area_struct *vma)
{
if (vma_is_anonymous(vma))
return true;
if (!vma->vm_file)
return false;
/*
* Reveal pagecache information only for non-anonymous mappings that
* correspond to the files the calling process could (if tried) open
* for writing; otherwise we'd be including shared non-exclusive
* mappings, which opens a side channel.
*/
return inode_owner_or_capable(file_inode(vma->vm_file)) ||
inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0;
}
static const struct mm_walk_ops mincore_walk_ops = {
.pmd_entry = mincore_pte_range,
.pte_hole = mincore_unmapped_range,
.hugetlb_entry = mincore_hugetlb,
};
/*
* Do a chunk of "sys_mincore()". We've already checked
* all the arguments, we hold the mmap semaphore: we should
* just return the amount of info we're asked for.
*/
static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
{
struct vm_area_struct *vma;
unsigned long end;
int err;
vma = find_vma(current->mm, addr);
if (!vma || addr < vma->vm_start)
return -ENOMEM;
end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
mm/mincore.c: make mincore() more conservative The semantics of what mincore() considers to be resident is not completely clear, but Linux has always (since 2.3.52, which is when mincore() was initially done) treated it as "page is available in page cache". That's potentially a problem, as that [in]directly exposes meta-information about pagecache / memory mapping state even about memory not strictly belonging to the process executing the syscall, opening possibilities for sidechannel attacks. Change the semantics of mincore() so that it only reveals pagecache information for non-anonymous mappings that belog to files that the calling process could (if it tried to) successfully open for writing; otherwise we'd be including shared non-exclusive mappings, which - is the sidechannel - is not the usecase for mincore(), as that's primarily used for data, not (shared) text [jkosina@suse.cz: v2] Link: http://lkml.kernel.org/r/20190312141708.6652-2-vbabka@suse.cz [mhocko@suse.com: restructure can_do_mincore() conditions] Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1903062342020.19912@cbobk.fhfr.pm Signed-off-by: Jiri Kosina <jkosina@suse.cz> Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Josh Snyder <joshs@netflix.com> Acked-by: Michal Hocko <mhocko@suse.com> Originally-by: Linus Torvalds <torvalds@linux-foundation.org> Originally-by: Dominique Martinet <asmadeus@codewreck.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dave Chinner <david@fromorbit.com> Cc: Kevin Easton <kevin@guarana.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: Cyril Hrubis <chrubis@suse.cz> Cc: Tejun Heo <tj@kernel.org> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Daniel Gruss <daniel@gruss.cc> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-05-15 06:41:38 +08:00
if (!can_do_mincore(vma)) {
unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
memset(vec, 1, pages);
return pages;
}
err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
if (err < 0)
return err;
return (end - addr) >> PAGE_SHIFT;
}
/*
* The mincore(2) system call.
*
* mincore() returns the memory residency status of the pages in the
* current process's address space specified by [addr, addr + len).
* The status is returned in a vector of bytes. The least significant
* bit of each byte is 1 if the referenced page is in memory, otherwise
* it is zero.
*
* Because the status of a page can change after mincore() checks it
* but before it returns to the application, the returned vector may
* contain stale information. Only locked pages are guaranteed to
* remain in memory.
*
* return values:
* zero - success
* -EFAULT - vec points to an illegal address
* -EINVAL - addr is not a multiple of PAGE_SIZE
* -ENOMEM - Addresses in the range [addr, addr + len] are
* invalid for the address space of this process, or
* specify one or more pages which are not currently
* mapped
* -EAGAIN - A kernel resource was temporarily unavailable.
*/
SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
unsigned char __user *, vec)
{
long retval;
unsigned long pages;
unsigned char *tmp;
start = untagged_addr(start);
/* Check the start address: needs to be page-aligned.. */
mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-04-01 20:29:47 +08:00
if (start & ~PAGE_MASK)
return -EINVAL;
/* ..and we need to be passed a valid user-space range */
Remove 'type' argument from access_ok() function Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-04 10:57:57 +08:00
if (!access_ok((void __user *) start, len))
return -ENOMEM;
/* This also avoids any overflows on PAGE_ALIGN */
pages = len >> PAGE_SHIFT;
pages += (offset_in_page(len)) != 0;
Remove 'type' argument from access_ok() function Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-04 10:57:57 +08:00
if (!access_ok(vec, pages))
return -EFAULT;
tmp = (void *) __get_free_page(GFP_USER);
if (!tmp)
return -EAGAIN;
retval = 0;
while (pages) {
/*
* Do at most PAGE_SIZE entries per iteration, due to
* the temporary buffer size.
*/
down_read(&current->mm->mmap_sem);
retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
up_read(&current->mm->mmap_sem);
if (retval <= 0)
break;
if (copy_to_user(vec, tmp, retval)) {
retval = -EFAULT;
break;
}
pages -= retval;
vec += retval;
start += retval << PAGE_SHIFT;
retval = 0;
}
free_page((unsigned long) tmp);
return retval;
}