linux-stable.git/fs/proc/base.c, branch v5.6 Linux kernel stable tree Merge branch 'work.openat2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-01-29T19:20:24+00:00 Linus Torvalds torvalds@linux-foundation.org 2020-01-29T19:20:24+00:00 6aee4badd8126f3a2b6d31c5e2db2439d316374f 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() 
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()
Merge branch 'x86-cache-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-01-28T20:00:29+00:00 Linus Torvalds torvalds@linux-foundation.org 2020-01-28T20:00:29+00:00 4244057c3da1dde07c0f338ea32fed6e79d6a657 Pull x86 resource control updates from Ingo Molnar: "The main change in this tree is the extension of the resctrl procfs ABI with a new file that helps tooling to navigate from tasks back to resctrl groups: /proc/{pid}/cpu_resctrl_groups. Also fix static key usage for certain feature combinations and simplify the task exit resctrl case" * 'x86-cache-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/resctrl: Add task resctrl information display x86/resctrl: Check monitoring static key in the MBM overflow handler x86/resctrl: Do not reconfigure exiting tasks 
Pull x86 resource control updates from Ingo Molnar:
 "The main change in this tree is the extension of the resctrl procfs
  ABI with a new file that helps tooling to navigate from tasks back to
  resctrl groups: /proc/{pid}/cpu_resctrl_groups.

  Also fix static key usage for certain feature combinations and
  simplify the task exit resctrl case"

* 'x86-cache-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Add task resctrl information display
  x86/resctrl: Check monitoring static key in the MBM overflow handler
  x86/resctrl: Do not reconfigure exiting tasks
x86/resctrl: Add task resctrl information display 2020-01-20T15:19:10+00:00 Chen Yu yu.c.chen@intel.com 2020-01-15T09:28:51+00:00 e79f15a4598c1f3f3f7f3319ca308c63c91fdaf2 Monitoring tools that want to find out which resctrl control and monitor groups a task belongs to must currently read the "tasks" file in every group until they locate the process ID. Add an additional file /proc/{pid}/cpu_resctrl_groups to provide this information: 1) res: mon: resctrl is not available. 2) res:/ mon: Task is part of the root resctrl control group, and it is not associated to any monitor group. 3) res:/ mon:mon0 Task is part of the root resctrl control group and monitor group mon0. 4) res:group0 mon: Task is part of resctrl control group group0, and it is not associated to any monitor group. 5) res:group0 mon:mon1 Task is part of resctrl control group group0 and monitor group mon1. Signed-off-by: Chen Yu <yu.c.chen@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Tested-by: Jinshi Chen <jinshi.chen@intel.com> Link: https://lkml.kernel.org/r/20200115092851.14761-1-yu.c.chen@intel.com 
Monitoring tools that want to find out which resctrl control and monitor
groups a task belongs to must currently read the "tasks" file in every
group until they locate the process ID.

Add an additional file /proc/{pid}/cpu_resctrl_groups to provide this
information:

1)   res:
     mon:

resctrl is not available.

2)   res:/
     mon:

Task is part of the root resctrl control group, and it is not associated
to any monitor group.

3)  res:/
    mon:mon0

Task is part of the root resctrl control group and monitor group mon0.

4)  res:group0
    mon:

Task is part of resctrl control group group0, and it is not associated
to any monitor group.

5) res:group0
   mon:mon1

Task is part of resctrl control group group0 and monitor group mon1.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Jinshi Chen <jinshi.chen@intel.com>
Link: https://lkml.kernel.org/r/20200115092851.14761-1-yu.c.chen@intel.com
fs/proc: Introduce /proc/pid/timens_offsets 2020-01-14T11:20:59+00:00 Andrei Vagin avagin@gmail.com 2019-11-12T01:27:16+00:00 04a8682a71becdb639ec9c0d82b315a2baef7a5d API to set time namespace offsets for children processes, i.e.: echo "$clockid $offset_sec $offset_nsec" > /proc/self/timens_offsets Co-developed-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Dmitry Safonov <dima@arista.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191112012724.250792-28-dima@arista.com 
API to set time namespace offsets for children processes, i.e.:
echo "$clockid $offset_sec $offset_nsec" > /proc/self/timens_offsets

Co-developed-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20191112012724.250792-28-dima@arista.com
namei: allow nd_jump_link() to produce errors 2019-12-09T00:09:38+00:00 Aleksa Sarai cyphar@cyphar.com 2019-12-06T14:13:28+00:00 1bc82070fa2763bdca626fa8bde72b35f11e8960 In preparation for LOOKUP_NO_MAGICLINKS, it's necessary to add the ability for nd_jump_link() to return an error which the corresponding get_link() caller must propogate back up to the VFS. Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> 
In preparation for LOOKUP_NO_MAGICLINKS, it's necessary to add the
ability for nd_jump_link() to return an error which the corresponding
get_link() caller must propogate back up to the VFS.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Merge branch 'proc-cmdline' (/proc/<pid>/cmdline fixes) 2019-07-16T17:37:27+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-07-16T17:37:27+00:00 2954152298c37804dab49d630aa959625b50cf64 This fixes two problems reported with the cmdline simplification and cleanup last year: - the setproctitle() special cases didn't quite match the original semantics, and it can be noticeable: https://lore.kernel.org/lkml/alpine.LNX.2.21.1904052326230.3249@kich.toxcorp.com/ - it could leak an uninitialized byte from the temporary buffer under the right (wrong) circustances: https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/ It rewrites the logic entirely, splitting it into two separate commits (and two separate functions) for the two different cases ("unedited cmdline" vs "setproctitle() has been used to change the command line"). * proc-cmdline: /proc/<pid>/cmdline: add back the setproctitle() special case /proc/<pid>/cmdline: remove all the special cases 
This fixes two problems reported with the cmdline simplification and
cleanup last year:

 - the setproctitle() special cases didn't quite match the original
   semantics, and it can be noticeable:

      https://lore.kernel.org/lkml/alpine.LNX.2.21.1904052326230.3249@kich.toxcorp.com/

 - it could leak an uninitialized byte from the temporary buffer under
   the right (wrong) circustances:

      https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/

It rewrites the logic entirely, splitting it into two separate commits
(and two separate functions) for the two different cases ("unedited
cmdline" vs "setproctitle() has been used to change the command line").

* proc-cmdline:
  /proc/<pid>/cmdline: add back the setproctitle() special case
  /proc/<pid>/cmdline: remove all the special cases
/proc/<pid>/cmdline: add back the setproctitle() special case 2019-07-16T16:57:52+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-07-13T21:27:14+00:00 d26d0cd97c88eb1a5704b42e41ab443406807810 This makes the setproctitle() special case very explicit indeed, and handles it with a separate helper function entirely. In the process, it re-instates the original semantics of simply stopping at the first NUL character when the original last NUL character is no longer there. [ The original semantics can still be seen in mm/util.c: get_cmdline() that is limited to a fixed-size buffer ] This makes the logic about when we use the string lengths etc much more obvious, and makes it easier to see what we do and what the two very different cases are. Note that even when we allow walking past the end of the argument array (because the setproctitle() might have overwritten and overflowed the original argv[] strings), we only allow it when it overflows into the environment region if it is immediately adjacent. [ Fixed for missing 'count' checks noted by Alexey Izbyshev ] Link: https://lore.kernel.org/lkml/alpine.LNX.2.21.1904052326230.3249@kich.toxcorp.com/ Fixes: 5ab827189965 ("fs/proc: simplify and clarify get_mm_cmdline() function") Cc: Jakub Jankowski <shasta@toxcorp.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Alexey Izbyshev <izbyshev@ispras.ru> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This makes the setproctitle() special case very explicit indeed, and
handles it with a separate helper function entirely.  In the process, it
re-instates the original semantics of simply stopping at the first NUL
character when the original last NUL character is no longer there.

[ The original semantics can still be seen in mm/util.c: get_cmdline()
  that is limited to a fixed-size buffer ]

This makes the logic about when we use the string lengths etc much more
obvious, and makes it easier to see what we do and what the two very
different cases are.

Note that even when we allow walking past the end of the argument array
(because the setproctitle() might have overwritten and overflowed the
original argv[] strings), we only allow it when it overflows into the
environment region if it is immediately adjacent.

[ Fixed for missing 'count' checks noted by Alexey Izbyshev ]

Link: https://lore.kernel.org/lkml/alpine.LNX.2.21.1904052326230.3249@kich.toxcorp.com/
Fixes: 5ab827189965 ("fs/proc: simplify and clarify get_mm_cmdline() function")
Cc: Jakub Jankowski <shasta@toxcorp.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
/proc/<pid>/cmdline: remove all the special cases 2019-07-16T16:57:52+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-07-13T20:40:13+00:00 3d712546d8ba9f25cdf080d79f90482aa4231ed4 Start off with a clean slate that only reads exactly from arg_start to arg_end, without any oddities. This simplifies the code and in the process removes the case that caused us to potentially leak an uninitialized byte from the temporary kernel buffer. Note that in order to start from scratch with an understandable base, this simplifies things _too_ much, and removes all the legacy logic to handle setproctitle() having changed the argument strings. We'll add back those special cases very differently in the next commit. Link: https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/ Fixes: f5b65348fd77 ("proc: fix missing final NUL in get_mm_cmdline() rewrite") Cc: Alexey Izbyshev <izbyshev@ispras.ru> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Start off with a clean slate that only reads exactly from arg_start to
arg_end, without any oddities.  This simplifies the code and in the
process removes the case that caused us to potentially leak an
uninitialized byte from the temporary kernel buffer.

Note that in order to start from scratch with an understandable base,
this simplifies things _too_ much, and removes all the legacy logic to
handle setproctitle() having changed the argument strings.

We'll add back those special cases very differently in the next commit.

Link: https://lore.kernel.org/lkml/20190712160913.17727-1-izbyshev@ispras.ru/
Fixes: f5b65348fd77 ("proc: fix missing final NUL in get_mm_cmdline() rewrite")
Cc: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
oom: decouple mems_allowed from oom_unkillable_task 2019-07-12T18:05:47+00:00 Shakeel Butt shakeelb@google.com 2019-07-12T04:00:31+00:00 ac311a14c682dcd8a120a6244d0542ec654e3d93 Commit ef08e3b4981a ("[PATCH] cpusets: confine oom_killer to mem_exclusive cpuset") introduces a heuristic where a potential oom-killer victim is skipped if the intersection of the potential victim and the current (the process triggered the oom) is empty based on the reason that killing such victim most probably will not help the current allocating process. However the commit 7887a3da753e ("[PATCH] oom: cpuset hint") changed the heuristic to just decrease the oom_badness scores of such potential victim based on the reason that the cpuset of such processes might have changed and previously they may have allocated memory on mems where the current allocating process can allocate from. Unintentionally 7887a3da753e ("[PATCH] oom: cpuset hint") introduced a side effect as the oom_badness is also exposed to the user space through /proc/[pid]/oom_score, so, readers with different cpusets can read different oom_score of the same process. Later, commit 6cf86ac6f36b ("oom: filter tasks not sharing the same cpuset") fixed the side effect introduced by 7887a3da753e by moving the cpuset intersection back to only oom-killer context and out of oom_badness. However the combination of ab290adbaf8f ("oom: make oom_unkillable_task() helper function") and 26ebc984913b ("oom: /proc/<pid>/oom_score treat kernel thread honestly") unintentionally brought back the cpuset intersection check into the oom_badness calculation function. Other than doing cpuset/mempolicy intersection from oom_badness, the memcg oom context is also doing cpuset/mempolicy intersection which is quite wrong and is caught by syzcaller with the following report: kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 28426 Comm: syz-executor.5 Not tainted 5.2.0-rc3-next-20190607 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline] RIP: 0010:has_intersects_mems_allowed mm/oom_kill.c:84 [inline] RIP: 0010:oom_unkillable_task mm/oom_kill.c:168 [inline] RIP: 0010:oom_unkillable_task+0x180/0x400 mm/oom_kill.c:155 Code: c1 ea 03 80 3c 02 00 0f 85 80 02 00 00 4c 8b a3 10 07 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8d 74 24 10 4c 89 f2 48 c1 ea 03 <80> 3c 02 00 0f 85 67 02 00 00 49 8b 44 24 10 4c 8d a0 68 fa ff ff RSP: 0018:ffff888000127490 EFLAGS: 00010a03 RAX: dffffc0000000000 RBX: ffff8880a4cd5438 RCX: ffffffff818dae9c RDX: 100000000c3cc602 RSI: ffffffff818dac8d RDI: 0000000000000001 RBP: ffff8880001274d0 R08: ffff888000086180 R09: ffffed1015d26be0 R10: ffffed1015d26bdf R11: ffff8880ae935efb R12: 8000000061e63007 R13: 0000000000000000 R14: 8000000061e63017 R15: 1ffff11000024ea6 FS: 00005555561f5940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000607304 CR3: 000000009237e000 CR4: 00000000001426f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace: oom_evaluate_task+0x49/0x520 mm/oom_kill.c:321 mem_cgroup_scan_tasks+0xcc/0x180 mm/memcontrol.c:1169 select_bad_process mm/oom_kill.c:374 [inline] out_of_memory mm/oom_kill.c:1088 [inline] out_of_memory+0x6b2/0x1280 mm/oom_kill.c:1035 mem_cgroup_out_of_memory+0x1ca/0x230 mm/memcontrol.c:1573 mem_cgroup_oom mm/memcontrol.c:1905 [inline] try_charge+0xfbe/0x1480 mm/memcontrol.c:2468 mem_cgroup_try_charge+0x24d/0x5e0 mm/memcontrol.c:6073 mem_cgroup_try_charge_delay+0x1f/0xa0 mm/memcontrol.c:6088 do_huge_pmd_wp_page_fallback+0x24f/0x1680 mm/huge_memory.c:1201 do_huge_pmd_wp_page+0x7fc/0x2160 mm/huge_memory.c:1359 wp_huge_pmd mm/memory.c:3793 [inline] __handle_mm_fault+0x164c/0x3eb0 mm/memory.c:4006 handle_mm_fault+0x3b7/0xa90 mm/memory.c:4053 do_user_addr_fault arch/x86/mm/fault.c:1455 [inline] __do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1521 do_page_fault+0x71/0x57d arch/x86/mm/fault.c:1552 page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1156 RIP: 0033:0x400590 Code: 06 e9 49 01 00 00 48 8b 44 24 10 48 0b 44 24 28 75 1f 48 8b 14 24 48 8b 7c 24 20 be 04 00 00 00 e8 f5 56 00 00 48 8b 74 24 08 <89> 06 e9 1e 01 00 00 48 8b 44 24 08 48 8b 14 24 be 04 00 00 00 8b RSP: 002b:00007fff7bc49780 EFLAGS: 00010206 RAX: 0000000000000001 RBX: 0000000000760000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 000000002000cffc RDI: 0000000000000001 RBP: fffffffffffffffe R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000760008 R13: 00000000004c55f2 R14: 0000000000000000 R15: 00007fff7bc499b0 Modules linked in: ---[ end trace a65689219582ffff ]--- RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline] RIP: 0010:has_intersects_mems_allowed mm/oom_kill.c:84 [inline] RIP: 0010:oom_unkillable_task mm/oom_kill.c:168 [inline] RIP: 0010:oom_unkillable_task+0x180/0x400 mm/oom_kill.c:155 Code: c1 ea 03 80 3c 02 00 0f 85 80 02 00 00 4c 8b a3 10 07 00 00 48 b8 00 00 00 00 00 fc ff df 4d 8d 74 24 10 4c 89 f2 48 c1 ea 03 <80> 3c 02 00 0f 85 67 02 00 00 49 8b 44 24 10 4c 8d a0 68 fa ff ff RSP: 0018:ffff888000127490 EFLAGS: 00010a03 RAX: dffffc0000000000 RBX: ffff8880a4cd5438 RCX: ffffffff818dae9c RDX: 100000000c3cc602 RSI: ffffffff818dac8d RDI: 0000000000000001 RBP: ffff8880001274d0 R08: ffff888000086180 R09: ffffed1015d26be0 R10: ffffed1015d26bdf R11: ffff8880ae935efb R12: 8000000061e63007 R13: 0000000000000000 R14: 8000000061e63017 R15: 1ffff11000024ea6 FS: 00005555561f5940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b2f823000 CR3: 000000009237e000 CR4: 00000000001426f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 The fix is to decouple the cpuset/mempolicy intersection check from oom_unkillable_task() and make sure cpuset/mempolicy intersection check is only done in the global oom context. [shakeelb@google.com: change function name and update comment] Link: http://lkml.kernel.org/r/20190628152421.198994-3-shakeelb@google.com Link: http://lkml.kernel.org/r/20190624212631.87212-3-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Reported-by: syzbot+d0fc9d3c166bc5e4a94b@syzkaller.appspotmail.com Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Paul Jackson <pj@sgi.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
Commit ef08e3b4981a ("[PATCH] cpusets: confine oom_killer to
mem_exclusive cpuset") introduces a heuristic where a potential
oom-killer victim is skipped if the intersection of the potential victim
and the current (the process triggered the oom) is empty based on the
reason that killing such victim most probably will not help the current
allocating process.

However the commit 7887a3da753e ("[PATCH] oom: cpuset hint") changed the
heuristic to just decrease the oom_badness scores of such potential
victim based on the reason that the cpuset of such processes might have
changed and previously they may have allocated memory on mems where the
current allocating process can allocate from.

Unintentionally 7887a3da753e ("[PATCH] oom: cpuset hint") introduced a
side effect as the oom_badness is also exposed to the user space through
/proc/[pid]/oom_score, so, readers with different cpusets can read
different oom_score of the same process.

Later, commit 6cf86ac6f36b ("oom: filter tasks not sharing the same
cpuset") fixed the side effect introduced by 7887a3da753e by moving the
cpuset intersection back to only oom-killer context and out of
oom_badness.  However the combination of ab290adbaf8f ("oom: make
oom_unkillable_task() helper function") and 26ebc984913b ("oom:
/proc/<pid>/oom_score treat kernel thread honestly") unintentionally
brought back the cpuset intersection check into the oom_badness
calculation function.

Other than doing cpuset/mempolicy intersection from oom_badness, the memcg
oom context is also doing cpuset/mempolicy intersection which is quite
wrong and is caught by syzcaller with the following report:

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 28426 Comm: syz-executor.5 Not tainted 5.2.0-rc3-next-20190607
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline]
RIP: 0010:has_intersects_mems_allowed mm/oom_kill.c:84 [inline]
RIP: 0010:oom_unkillable_task mm/oom_kill.c:168 [inline]
RIP: 0010:oom_unkillable_task+0x180/0x400 mm/oom_kill.c:155
Code: c1 ea 03 80 3c 02 00 0f 85 80 02 00 00 4c 8b a3 10 07 00 00 48 b8 00
00 00 00 00 fc ff df 4d 8d 74 24 10 4c 89 f2 48 c1 ea 03 <80> 3c 02 00 0f
85 67 02 00 00 49 8b 44 24 10 4c 8d a0 68 fa ff ff
RSP: 0018:ffff888000127490 EFLAGS: 00010a03
RAX: dffffc0000000000 RBX: ffff8880a4cd5438 RCX: ffffffff818dae9c
RDX: 100000000c3cc602 RSI: ffffffff818dac8d RDI: 0000000000000001
RBP: ffff8880001274d0 R08: ffff888000086180 R09: ffffed1015d26be0
R10: ffffed1015d26bdf R11: ffff8880ae935efb R12: 8000000061e63007
R13: 0000000000000000 R14: 8000000061e63017 R15: 1ffff11000024ea6
FS:  00005555561f5940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000607304 CR3: 000000009237e000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
  oom_evaluate_task+0x49/0x520 mm/oom_kill.c:321
  mem_cgroup_scan_tasks+0xcc/0x180 mm/memcontrol.c:1169
  select_bad_process mm/oom_kill.c:374 [inline]
  out_of_memory mm/oom_kill.c:1088 [inline]
  out_of_memory+0x6b2/0x1280 mm/oom_kill.c:1035
  mem_cgroup_out_of_memory+0x1ca/0x230 mm/memcontrol.c:1573
  mem_cgroup_oom mm/memcontrol.c:1905 [inline]
  try_charge+0xfbe/0x1480 mm/memcontrol.c:2468
  mem_cgroup_try_charge+0x24d/0x5e0 mm/memcontrol.c:6073
  mem_cgroup_try_charge_delay+0x1f/0xa0 mm/memcontrol.c:6088
  do_huge_pmd_wp_page_fallback+0x24f/0x1680 mm/huge_memory.c:1201
  do_huge_pmd_wp_page+0x7fc/0x2160 mm/huge_memory.c:1359
  wp_huge_pmd mm/memory.c:3793 [inline]
  __handle_mm_fault+0x164c/0x3eb0 mm/memory.c:4006
  handle_mm_fault+0x3b7/0xa90 mm/memory.c:4053
  do_user_addr_fault arch/x86/mm/fault.c:1455 [inline]
  __do_page_fault+0x5ef/0xda0 arch/x86/mm/fault.c:1521
  do_page_fault+0x71/0x57d arch/x86/mm/fault.c:1552
  page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1156
RIP: 0033:0x400590
Code: 06 e9 49 01 00 00 48 8b 44 24 10 48 0b 44 24 28 75 1f 48 8b 14 24 48
8b 7c 24 20 be 04 00 00 00 e8 f5 56 00 00 48 8b 74 24 08 <89> 06 e9 1e 01
00 00 48 8b 44 24 08 48 8b 14 24 be 04 00 00 00 8b
RSP: 002b:00007fff7bc49780 EFLAGS: 00010206
RAX: 0000000000000001 RBX: 0000000000760000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 000000002000cffc RDI: 0000000000000001
RBP: fffffffffffffffe R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000075 R11: 0000000000000246 R12: 0000000000760008
R13: 00000000004c55f2 R14: 0000000000000000 R15: 00007fff7bc499b0
Modules linked in:
---[ end trace a65689219582ffff ]---
RIP: 0010:__read_once_size include/linux/compiler.h:194 [inline]
RIP: 0010:has_intersects_mems_allowed mm/oom_kill.c:84 [inline]
RIP: 0010:oom_unkillable_task mm/oom_kill.c:168 [inline]
RIP: 0010:oom_unkillable_task+0x180/0x400 mm/oom_kill.c:155
Code: c1 ea 03 80 3c 02 00 0f 85 80 02 00 00 4c 8b a3 10 07 00 00 48 b8 00
00 00 00 00 fc ff df 4d 8d 74 24 10 4c 89 f2 48 c1 ea 03 <80> 3c 02 00 0f
85 67 02 00 00 49 8b 44 24 10 4c 8d a0 68 fa ff ff
RSP: 0018:ffff888000127490 EFLAGS: 00010a03
RAX: dffffc0000000000 RBX: ffff8880a4cd5438 RCX: ffffffff818dae9c
RDX: 100000000c3cc602 RSI: ffffffff818dac8d RDI: 0000000000000001
RBP: ffff8880001274d0 R08: ffff888000086180 R09: ffffed1015d26be0
R10: ffffed1015d26bdf R11: ffff8880ae935efb R12: 8000000061e63007
R13: 0000000000000000 R14: 8000000061e63017 R15: 1ffff11000024ea6
FS:  00005555561f5940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f823000 CR3: 000000009237e000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600

The fix is to decouple the cpuset/mempolicy intersection check from
oom_unkillable_task() and make sure cpuset/mempolicy intersection check is
only done in the global oom context.

[shakeelb@google.com: change function name and update comment]
  Link: http://lkml.kernel.org/r/20190628152421.198994-3-shakeelb@google.com
Link: http://lkml.kernel.org/r/20190624212631.87212-3-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reported-by: syzbot+d0fc9d3c166bc5e4a94b@syzkaller.appspotmail.com
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Paul Jackson <pj@sgi.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm, oom: remove redundant task_in_mem_cgroup() check 2019-07-12T18:05:47+00:00 Shakeel Butt shakeelb@google.com 2019-07-12T04:00:26+00:00 6ba749ee78ef42ffdf4b95c042fc574a37d229d9 oom_unkillable_task() can be called from three different contexts i.e. global OOM, memcg OOM and oom_score procfs interface. At the moment oom_unkillable_task() does a task_in_mem_cgroup() check on the given process. Since there is no reason to perform task_in_mem_cgroup() check for global OOM and oom_score procfs interface, those contexts provide NULL memcg and skips the task_in_mem_cgroup() check. However for memcg OOM context, the oom_unkillable_task() is always called from mem_cgroup_scan_tasks() and thus task_in_mem_cgroup() check becomes redundant and effectively dead code. So, just remove the task_in_mem_cgroup() check altogether. Link: http://lkml.kernel.org/r/20190624212631.87212-2-shakeelb@google.com Signed-off-by: Shakeel Butt <shakeelb@google.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: David Rientjes <rientjes@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Paul Jackson <pj@sgi.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
oom_unkillable_task() can be called from three different contexts i.e.
global OOM, memcg OOM and oom_score procfs interface.  At the moment
oom_unkillable_task() does a task_in_mem_cgroup() check on the given
process.  Since there is no reason to perform task_in_mem_cgroup()
check for global OOM and oom_score procfs interface, those contexts
provide NULL memcg and skips the task_in_mem_cgroup() check.  However
for memcg OOM context, the oom_unkillable_task() is always called from
mem_cgroup_scan_tasks() and thus task_in_mem_cgroup() check becomes
redundant and effectively dead code.  So, just remove the
task_in_mem_cgroup() check altogether.

Link: http://lkml.kernel.org/r/20190624212631.87212-2-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Paul Jackson <pj@sgi.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>