Commit Graph

12 Commits

Author SHA1 Message Date
David Hildenbrand bbcd53c960 drivers/char: remove /dev/kmem for good
Patch series "drivers/char: remove /dev/kmem for good".

Exploring /dev/kmem and /dev/mem in the context of memory hot(un)plug and
memory ballooning, I started questioning the existence of /dev/kmem.

Comparing it with the /proc/kcore implementation, it does not seem to be
able to deal with things like

a) Pages unmapped from the direct mapping (e.g., to be used by secretmem)
  -> kern_addr_valid(). virt_addr_valid() is not sufficient.

b) Special cases like gart aperture memory that is not to be touched
  -> mem_pfn_is_ram()

Unless I am missing something, it's at least broken in some cases and might
fault/crash the machine.

Looks like its existence has been questioned before in 2005 and 2010 [1],
after ~11 additional years, it might make sense to revive the discussion.

CONFIG_DEVKMEM is only enabled in a single defconfig (on purpose or by
mistake?).  All distributions disable it: in Ubuntu it has been disabled
for more than 10 years, in Debian since 2.6.31, in Fedora at least
starting with FC3, in RHEL starting with RHEL4, in SUSE starting from
15sp2, and OpenSUSE has it disabled as well.

1) /dev/kmem was popular for rootkits [2] before it got disabled
   basically everywhere. Ubuntu documents [3] "There is no modern user of
   /dev/kmem any more beyond attackers using it to load kernel rootkits.".
   RHEL documents in a BZ [5] "it served no practical purpose other than to
   serve as a potential security problem or to enable binary module drivers
   to access structures/functions they shouldn't be touching"

2) /proc/kcore is a decent interface to have a controlled way to read
   kernel memory for debugging puposes. (will need some extensions to
   deal with memory offlining/unplug, memory ballooning, and poisoned
   pages, though)

3) It might be useful for corner case debugging [1]. KDB/KGDB might be a
   better fit, especially, to write random memory; harder to shoot
   yourself into the foot.

4) "Kernel Memory Editor" [4] hasn't seen any updates since 2000 and seems
   to be incompatible with 64bit [1]. For educational purposes,
   /proc/kcore might be used to monitor value updates -- or older
   kernels can be used.

5) It's broken on arm64, and therefore, completely disabled there.

Looks like it's essentially unused and has been replaced by better
suited interfaces for individual tasks (/proc/kcore, KDB/KGDB). Let's
just remove it.

[1] https://lwn.net/Articles/147901/
[2] https://www.linuxjournal.com/article/10505
[3] https://wiki.ubuntu.com/Security/Features#A.2Fdev.2Fkmem_disabled
[4] https://sourceforge.net/projects/kme/
[5] https://bugzilla.redhat.com/show_bug.cgi?id=154796

Link: https://lkml.kernel.org/r/20210324102351.6932-1-david@redhat.com
Link: https://lkml.kernel.org/r/20210324102351.6932-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Alexander A. Klimov" <grandmaster@al2klimov.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Chris Zankel <chris@zankel.net>
Cc: Corentin Labbe <clabbe@baylibre.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Gregory Clement <gregory.clement@bootlin.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hillf Danton <hdanton@sina.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: James Troup <james.troup@canonical.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kairui Song <kasong@redhat.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Niklas Schnelle <schnelle@linux.ibm.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: openrisc@lists.librecores.org
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Pavel Machek (CIP)" <pavel@denx.de>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Pierre Morel <pmorel@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Rich Felker <dalias@libc.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: sparclinux@vger.kernel.org
Cc: Stafford Horne <shorne@gmail.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Theodore Dubois <tblodt@icloud.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: William Cohen <wcohen@redhat.com>
Cc: Xiaoming Ni <nixiaoming@huawei.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-05-07 00:26:34 -07:00
Alexey Brodkin 3337d5cfe5 configs: get rid of obsolete CONFIG_ENABLE_WARN_DEPRECATED
This Kconfig option was removed during v4.19 development in commit
771c035372 ("deprecate the '__deprecated' attribute warnings entirely
and for good") so there's no point to keep it in defconfigs any longer.

FWIW defconfigs were patched with:
--------------------------->8----------------------
find . -name *_defconfig -exec sed -i '/CONFIG_ENABLE_WARN_DEPRECATED/d' {} \;
--------------------------->8----------------------

Link: http://lkml.kernel.org/r/20190128152434.41969-1-abrodkin@synopsys.com
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-03-07 18:32:02 -08:00
Krzysztof Kozlowski 229cf16d3c sh: defconfig: cleanup from old Kconfig options
Remove old, dead Kconfig options (in order appearing in this commit):
 - EXPERIMENTAL is gone since v3.9;
 - INET_LRO: commit 7bbf3cae65 ("ipv4: Remove inet_lro library");
 - MTD_CONCAT: commit f53fdebcc3 ("mtd: drop MTD_CONCAT from Kconfig
   entirely");
 - MTD_PARTITIONS: commit 6a8a98b22b ("mtd: kill
   CONFIG_MTD_PARTITIONS");
 - MTD_CHAR: commit 660685d9d1 ("mtd: merge mtdchar module with
   mtdcore");
 - NETDEV_1000 and NETDEV_10000: commit f860b0522f ("drivers/net:
   Kconfig and Makefile cleanup"); NET_ETHERNET should be replaced with
   just ETHERNET but that is separate change;
 - HID_SUPPORT: commit 1f41a6a994 ("HID: Fix the generic Kconfig
   options");
 - RCU_CPU_STALL_DETECTOR: commit a00e0d714f ("rcu: Remove conditional
   compilation for RCU CPU stall warnings");
 - SYSCTL_SYSCALL_CHECK: commit 7c60c48f58 ("sysctl: Improve the
   sysctl sanity checks");
 - VIDEO_OUTPUT_CONTROL: commit f167a64e9d ("video / output: Drop
   display output class support");
 - MISC_DEVICES: commit 7c5763b845 ("drivers: misc: Remove
   MISC_DEVICES config option");
 - AUTOFS_FS: commit 561c5cf923 ("staging: Remove autofs3");
 - IP_NF_QUEUE: commit 3dd6664fac ("netfilter: remove unused "config
   IP_NF_QUEUE"");
 - USB_DEVICE_CLASS: commit 007bab9132 ("USB: remove
   CONFIG_USB_DEVICE_CLASS");
 - USB_LIBUSUAL: commit f61870ee6f ("usb: remove libusual");
 - DISPLAY_SUPPORT: commit 5a6b5e02d6 ("fbdev: remove display
   subsystem");
 - IP_NF_TARGET_ULOG: commit d4da843e6f ("netfilter: kill remnants of
   ulog targets");
 - IP6_NF_QUEUE: commit d16cf20e2f ("netfilter: remove ip_queue
   support");
 - IP6_NF_TARGET_LOG: commit 6939c33a75 ("netfilter: merge ipt_LOG and
   ip6_LOG into xt_LOG");

Link: http://lkml.kernel.org/r/1500526846-4072-1-git-send-email-krzk@kernel.org
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-08 18:26:51 -07:00
Sam Ravnborg 8b1bb90701 defconfig reduction
Use the defconfig files generated by "make savedefconfig" for
remaining defconfig files.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
2010-08-14 22:26:53 +02:00
Paul Mundt 4d0956b8f5 sh: update defconfigs.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2010-05-18 18:18:28 +09:00
Paul Mundt 7dbcd8c55f sh: update defconfigs.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2010-01-04 15:38:50 +09:00
Paul Mundt 5d65498b09 sh: update defconfigs.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2009-09-25 11:53:02 +09:00
Paul Mundt b7d3740ace sh: defconfig updates.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2009-06-18 13:28:09 +09:00
Paul Mundt fc4967b8c6 sh: update defconfigs for PCI changes.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2009-04-27 14:06:26 +09:00
Paul Mundt 53a52abcf3 sh: update defconfigs.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2009-04-02 22:02:26 +09:00
Paul Mundt 5e8766f1c1 sh: update defconfigs.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2009-01-21 17:44:16 +09:00
Paul Mundt 8c197c3afb sh: Add a simple edosk7705_defconfig for build testing.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2008-12-22 18:44:46 +09:00