OpenCloudOS-Kernel/fs/proc
Linus Torvalds 6aee4badd8 Merge branch 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull openat2 support from Al Viro:
 "This is the openat2() series from Aleksa Sarai.

  I'm afraid that the rest of namei stuff will have to wait - it got
  zero review the last time I'd posted #work.namei, and there had been a
  leak in the posted series I'd caught only last weekend. I was going to
  repost it on Monday, but the window opened and the odds of getting any
  review during that... Oh, well.

  Anyway, openat2 part should be ready; that _did_ get sane amount of
  review and public testing, so here it comes"

From Aleksa's description of the series:
 "For a very long time, extending openat(2) with new features has been
  incredibly frustrating. This stems from the fact that openat(2) is
  possibly the most famous counter-example to the mantra "don't silently
  accept garbage from userspace" -- it doesn't check whether unknown
  flags are present[1].

  This means that (generally) the addition of new flags to openat(2) has
  been fraught with backwards-compatibility issues (O_TMPFILE has to be
  defined as __O_TMPFILE|O_DIRECTORY|[O_RDWR or O_WRONLY] to ensure old
  kernels gave errors, since it's insecure to silently ignore the
  flag[2]). All new security-related flags therefore have a tough road
  to being added to openat(2).

  Furthermore, the need for some sort of control over VFS's path
  resolution (to avoid malicious paths resulting in inadvertent
  breakouts) has been a very long-standing desire of many userspace
  applications.

  This patchset is a revival of Al Viro's old AT_NO_JUMPS[3] patchset
  (which was a variant of David Drysdale's O_BENEATH patchset[4] which
  was a spin-off of the Capsicum project[5]) with a few additions and
  changes made based on the previous discussion within [6] as well as
  others I felt were useful.

  In line with the conclusions of the original discussion of
  AT_NO_JUMPS, the flag has been split up into separate flags. However,
  instead of being an openat(2) flag it is provided through a new
  syscall openat2(2) which provides several other improvements to the
  openat(2) interface (see the patch description for more details). The
  following new LOOKUP_* flags are added:

  LOOKUP_NO_XDEV:

     Blocks all mountpoint crossings (upwards, downwards, or through
     absolute links). Absolute pathnames alone in openat(2) do not
     trigger this. Magic-link traversal which implies a vfsmount jump is
     also blocked (though magic-link jumps on the same vfsmount are
     permitted).

  LOOKUP_NO_MAGICLINKS:

     Blocks resolution through /proc/$pid/fd-style links. This is done
     by blocking the usage of nd_jump_link() during resolution in a
     filesystem. The term "magic-links" is used to match with the only
     reference to these links in Documentation/, but I'm happy to change
     the name.

     It should be noted that this is different to the scope of
     ~LOOKUP_FOLLOW in that it applies to all path components. However,
     you can do openat2(NO_FOLLOW|NO_MAGICLINKS) on a magic-link and it
     will *not* fail (assuming that no parent component was a
     magic-link), and you will have an fd for the magic-link.

     In order to correctly detect magic-links, the introduction of a new
     LOOKUP_MAGICLINK_JUMPED state flag was required.

  LOOKUP_BENEATH:

     Disallows escapes to outside the starting dirfd's
     tree, using techniques such as ".." or absolute links. Absolute
     paths in openat(2) are also disallowed.

     Conceptually this flag is to ensure you "stay below" a certain
     point in the filesystem tree -- but this requires some additional
     to protect against various races that would allow escape using
     "..".

     Currently LOOKUP_BENEATH implies LOOKUP_NO_MAGICLINKS, because it
     can trivially beam you around the filesystem (breaking the
     protection). In future, there might be similar safety checks done
     as in LOOKUP_IN_ROOT, but that requires more discussion.

  In addition, two new flags are added that expand on the above ideas:

  LOOKUP_NO_SYMLINKS:

     Does what it says on the tin. No symlink resolution is allowed at
     all, including magic-links. Just as with LOOKUP_NO_MAGICLINKS this
     can still be used with NOFOLLOW to open an fd for the symlink as
     long as no parent path had a symlink component.

  LOOKUP_IN_ROOT:

     This is an extension of LOOKUP_BENEATH that, rather than blocking
     attempts to move past the root, forces all such movements to be
     scoped to the starting point. This provides chroot(2)-like
     protection but without the cost of a chroot(2) for each filesystem
     operation, as well as being safe against race attacks that
     chroot(2) is not.

     If a race is detected (as with LOOKUP_BENEATH) then an error is
     generated, and similar to LOOKUP_BENEATH it is not permitted to
     cross magic-links with LOOKUP_IN_ROOT.

     The primary need for this is from container runtimes, which
     currently need to do symlink scoping in userspace[7] when opening
     paths in a potentially malicious container.

     There is a long list of CVEs that could have bene mitigated by
     having RESOLVE_THIS_ROOT (such as CVE-2017-1002101,
     CVE-2017-1002102, CVE-2018-15664, and CVE-2019-5736, just to name a
     few).

  In order to make all of the above more usable, I'm working on
  libpathrs[8] which is a C-friendly library for safe path resolution.
  It features a userspace-emulated backend if the kernel doesn't support
  openat2(2). Hopefully we can get userspace to switch to using it, and
  thus get openat2(2) support for free once it's ready.

  Future work would include implementing things like
  RESOLVE_NO_AUTOMOUNT and possibly a RESOLVE_NO_REMOTE (to allow
  programs to be sure they don't hit DoSes though stale NFS handles)"

* 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  Documentation: path-lookup: include new LOOKUP flags
  selftests: add openat2(2) selftests
  open: introduce openat2(2) syscall
  namei: LOOKUP_{IN_ROOT,BENEATH}: permit limited ".." resolution
  namei: LOOKUP_IN_ROOT: chroot-like scoped resolution
  namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution
  namei: LOOKUP_NO_XDEV: block mountpoint crossing
  namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution
  namei: LOOKUP_NO_SYMLINKS: block symlink resolution
  namei: allow set_root() to produce errors
  namei: allow nd_jump_link() to produce errors
  nsfs: clean-up ns_get_path() signature to return int
  namei: only return -ECHILD from follow_dotdot_rcu()
2020-01-29 11:20:24 -08:00
..
Kconfig x86/resctrl: Add task resctrl information display 2020-01-20 16:19:10 +01:00
Makefile proc: : uninline name_to_int() 2017-11-17 16:10:00 -08:00
array.c time: Rename tsk->real_start_time to ->start_boottime 2019-11-13 11:09:49 +01:00
base.c Merge branch 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-01-29 11:20:24 -08:00
cmdline.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
consoles.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 191 2019-05-30 11:29:21 -07:00
cpuinfo.c x86 / CPU: Always show current CPU frequency in /proc/cpuinfo 2017-11-15 19:46:50 +01:00
devices.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
fd.c proc: use "unsigned int" in proc_fill_cache() 2018-06-07 17:34:38 -07:00
fd.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
generic.c fs/proc/generic.c: delete useless "len" variable 2019-12-04 19:44:11 -08:00
inode.c fs/proc/inode.c: use typeof_member() macro 2019-07-16 19:23:21 -07:00
internal.h fs/proc/internal.h: shuffle "struct pde_opener" 2019-12-04 19:44:11 -08:00
interrupts.c proc: introduce proc_create_seq{,_data} 2018-05-16 07:23:35 +02:00
kcore.c lockdown: Print current->comm in restriction messages 2019-08-19 21:54:17 -07:00
kmsg.c vfs: do bulk POLL* -> EPOLL* replacement 2018-02-11 14:34:03 -08:00
loadavg.c sched: loadavg: consolidate LOAD_INT, LOAD_FRAC, CALC_LOAD 2018-10-26 16:26:32 -07:00
meminfo.c proc/meminfo: fix output alignment 2019-10-19 06:32:32 -04:00
namespaces.c Merge branch 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-01-29 11:20:24 -08:00
nommu.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
page.c fs/proc/page.c: don't access uninitialized memmaps in fs/proc/page.c 2019-10-19 06:32:31 -04:00
proc_net.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
proc_sysctl.c proc/sysctl: add shared variables for range check 2019-07-18 17:08:07 -07:00
proc_tty.c tty: replace ->proc_fops with ->proc_show 2018-05-16 07:24:30 +02:00
root.c new helper: get_tree_keyed() 2019-09-05 14:34:22 -04:00
self.c fs/proc/self.c: code cleanup for proc_setup_self() 2019-03-05 21:07:21 -08:00
softirqs.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
stat.c sched/cputime, proc/stat: Fix incorrect guest nice cpustat value 2019-12-11 07:09:58 +01:00
task_mmu.c mm,thp: stats for file backed THP 2019-09-24 15:54:11 -07:00
task_nommu.c proc: use down_read_killable mmap_sem for /proc/pid/maps 2019-07-12 11:05:46 -07:00
thread_self.c fs/proc/thread_self.c: code cleanup for proc_setup_thread_self() 2019-03-05 21:07:21 -08:00
uptime.c fs/proc: Respect boottime inside time namespace for /proc/uptime 2020-01-14 12:20:56 +01:00
util.c fs/proc/util.c: include fs/proc/internal.h for name_to_int() 2019-01-04 13:13:45 -08:00
version.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
vmcore.c fs/core/vmcore: Move sev_active() reference to x86 arch code 2019-08-09 22:52:10 +10:00