linux-toradex.git/kernel/signal.c, branch v5.3-rc1

signal: simplify set_user_sigmask/restore_user_sigmask

2019-07-17T02:23:24+00:00

task->saved_sigmask and ->restore_sigmask are only used in the ret-from-
syscall paths.  This means that set_user_sigmask() can save ->blocked in
->saved_sigmask and do set_restore_sigmask() to indicate that ->blocked
was modified.

This way the callers do not need 2 sigset_t's passed to set/restore and
restore_user_sigmask() renamed to restore_saved_sigmask_unless() turns
into the trivial helper which just calls restore_saved_sigmask().

Link: http://lkml.kernel.org/r/20190606113206.GA9464@redhat.com
Signed-off-by: Oleg Nesterov 
Cc: Deepa Dinamani 
Cc: Arnd Bergmann 
Cc: Jens Axboe 
Cc: Davidlohr Bueso 
Cc: Eric Wong 
Cc: Jason Baron 
Cc: Thomas Gleixner 
Cc: Al Viro 
Cc: Eric W. Biederman 
Cc: David Laight 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'pidfd-updates-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

2019-07-11T05:17:21+00:00

Pull pidfd updates from Christian Brauner:
"This adds two main features.

- First, it adds polling support for pidfds. This allows process
managers to know when a (non-parent) process dies in a race-free
way.

The notification mechanism used follows the same logic that is
currently used when the parent of a task is notified of a child's
death. With this patchset it is possible to put pidfds in an
{e}poll loop and get reliable notifications for process (i.e.
thread-group) exit.

- The second feature compliments the first one by making it possible
to retrieve pollable pidfds for processes that were not created
using CLONE_PIDFD.

A lot of processes get created with traditional PID-based calls
such as fork() or clone() (without CLONE_PIDFD). For these
processes a caller can currently not create a pollable pidfd. This
is a problem for Android's low memory killer (LMK) and service
managers such as systemd.

Both patchsets are accompanied by selftests.

It's perhaps worth noting that the work done so far and the work done
in this branch for pidfd_open() and polling support do already see
some adoption:

- Android is in the process of backporting this work to all their LTS
kernels [1]

- Service managers make use of pidfd_send_signal but will need to
wait until we enable waiting on pidfds for full adoption.

- And projects I maintain make use of both pidfd_send_signal and
CLONE_PIDFD [2] and will use polling support and pidfd_open() too"

[1] https://android-review.googlesource.com/q/topic:%22pidfd+polling+support+4.9+backport%22
https://android-review.googlesource.com/q/topic:%22pidfd+polling+support+4.14+backport%22
https://android-review.googlesource.com/q/topic:%22pidfd+polling+support+4.19+backport%22

[2] https://github.com/lxc/lxc/blob/aab6e3eb73c343231cdde775db938994fc6f2803/src/lxc/start.c#L1753

* tag 'pidfd-updates-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
tests: add pidfd_open() tests
arch: wire-up pidfd_open()
pid: add pidfd_open()
pidfd: add polling selftests
pidfd: add polling support

Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2019-07-09T04:48:15+00:00

Pull force_sig() argument change from Eric Biederman:
 "A source of error over the years has been that force_sig has taken a
  task parameter when it is only safe to use force_sig with the current
  task.

  The force_sig function is built for delivering synchronous signals
  such as SIGSEGV where the userspace application caused a synchronous
  fault (such as a page fault) and the kernel responded with a signal.

  Because the name force_sig does not make this clear, and because the
  force_sig takes a task parameter the function force_sig has been
  abused for sending other kinds of signals over the years. Slowly those
  have been fixed when the oopses have been tracked down.

  This set of changes fixes the remaining abusers of force_sig and
  carefully rips out the task parameter from force_sig and friends
  making this kind of error almost impossible in the future"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (27 commits)
  signal/x86: Move tsk inside of CONFIG_MEMORY_FAILURE in do_sigbus
  signal: Remove the signal number and task parameters from force_sig_info
  signal: Factor force_sig_info_to_task out of force_sig_info
  signal: Generate the siginfo in force_sig
  signal: Move the computation of force into send_signal and correct it.
  signal: Properly set TRACE_SIGNAL_LOSE_INFO in __send_signal
  signal: Remove the task parameter from force_sig_fault
  signal: Use force_sig_fault_to_task for the two calls that don't deliver to current
  signal: Explicitly call force_sig_fault on current
  signal/unicore32: Remove tsk parameter from __do_user_fault
  signal/arm: Remove tsk parameter from __do_user_fault
  signal/arm: Remove tsk parameter from ptrace_break
  signal/nds32: Remove tsk parameter from send_sigtrap
  signal/riscv: Remove tsk parameter from do_trap
  signal/sh: Remove tsk parameter from force_sig_info_fault
  signal/um: Remove task parameter from send_sigtrap
  signal/x86: Remove task parameter from send_sigtrap
  signal: Remove task parameter from force_sig_mceerr
  signal: Remove task parameter from force_sig
  signal: Remove task parameter from force_sigsegv
  ...

Merge tag 'audit-pr-20190702' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit

2019-07-09T01:55:42+00:00

Pull audit updates from Paul Moore:
 "This pull request is a bit early, but with some vacation time coming
  up I wanted to send this out now just in case the remote Internet Gods
  decide not to smile on me once the merge window opens. The patchset
  for v5.3 is pretty minor this time, the highlights include:

   - When the audit daemon is sent a signal, ensure we deliver
     information about the sender even when syscall auditing is not
     enabled/supported.

   - Add the ability to filter audit records based on network address
     family.

   - Tighten the audit field filtering restrictions on string based
     fields.

   - Cleanup the audit field filtering verification code.

   - Remove a few BUG() calls from the audit code"

* tag 'audit-pr-20190702' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
  audit: remove the BUG() calls in the audit rule comparison functions
  audit: enforce op for string fields
  audit: add saddr_fam filter field
  audit: re-structure audit field valid checks
  audit: deliver signal_info regarless of syscall

signal: remove the wrong signal_pending() check in restore_user_sigmask()

2019-06-29T08:43:45+00:00

This is the minimal fix for stable, I'll send cleanups later.

Commit 854a6ed56839 ("signal: Add restore_user_sigmask()") introduced
the visible change which breaks user-space: a signal temporary unblocked
by set_user_sigmask() can be delivered even if the caller returns
success or timeout.

Change restore_user_sigmask() to accept the additional "interrupted"
argument which should be used instead of signal_pending() check, and
update the callers.

Eric said:

: For clarity.  I don't think this is required by posix, or fundamentally to
: remove the races in select.  It is what linux has always done and we have
: applications who care so I agree this fix is needed.
:
: Further in any case where the semantic change that this patch rolls back
: (aka where allowing a signal to be delivered and the select like call to
: complete) would be advantage we can do as well if not better by using
: signalfd.
:
: Michael is there any chance we can get this guarantee of the linux
: implementation of pselect and friends clearly documented.  The guarantee
: that if the system call completes successfully we are guaranteed that no
: signal that is unblocked by using sigmask will be delivered?

Link: http://lkml.kernel.org/r/20190604134117.GA29963@redhat.com
Fixes: 854a6ed56839a40f6b5d02a2962f48841482eec4 ("signal: Add restore_user_sigmask()")
Signed-off-by: Oleg Nesterov 
Reported-by: Eric Wong 
Tested-by: Eric Wong 
Acked-by: "Eric W. Biederman" 
Acked-by: Arnd Bergmann 
Acked-by: Deepa Dinamani 
Cc: Michael Kerrisk 
Cc: Jens Axboe 
Cc: Davidlohr Bueso 
Cc: Jason Baron 
Cc: Thomas Gleixner 
Cc: Al Viro 
Cc: David Laight 
Cc: 	[5.0+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pidfd: add polling support

2019-06-28T10:17:55+00:00

This patch adds polling support to pidfd.

Android low memory killer (LMK) needs to know when a process dies once
it is sent the kill signal. It does so by checking for the existence of
/proc/pid which is both racy and slow. For example, if a PID is reused
between when LMK sends a kill signal and checks for existence of the
PID, since the wrong PID is now possibly checked for existence.
Using the polling support, LMK will be able to get notified when a process
exists in race-free and fast way, and allows the LMK to do other things
(such as by polling on other fds) while awaiting the process being killed
to die.

For notification to polling processes, we follow the same existing
mechanism in the kernel used when the parent of the task group is to be
notified of a child's death (do_notify_parent). This is precisely when the
tasks waiting on a poll of pidfd are also awakened in this patch.

We have decided to include the waitqueue in struct pid for the following
reasons:
1. The wait queue has to survive for the lifetime of the poll. Including
   it in task_struct would not be option in this case because the task can
   be reaped and destroyed before the poll returns.

2. By including the struct pid for the waitqueue means that during
   de_thread(), the new thread group leader automatically gets the new
   waitqueue/pid even though its task_struct is different.

Appropriate test cases are added in the second patch to provide coverage of
all the cases the patch is handling.

Cc: Andy Lutomirski 
Cc: Steven Rostedt 
Cc: Daniel Colascione 
Cc: Jann Horn 
Cc: Tim Murray 
Cc: Jonathan Kowalski 
Cc: Linus Torvalds 
Cc: Al Viro 
Cc: Kees Cook 
Cc: David Howells 
Cc: Oleg Nesterov 
Cc: kernel-team@android.com
Reviewed-by: Oleg Nesterov 
Co-developed-by: Daniel Colascione 
Signed-off-by: Daniel Colascione 
Signed-off-by: Joel Fernandes (Google) 
Signed-off-by: Christian Brauner

signal: improve comments

2019-06-05T13:06:07+00:00

Improve the comments for pidfd_send_signal().
First, the comment still referred to a file descriptor for a process as a
"task file descriptor" which stems from way back at the beginning of the
discussion. Replace this with "pidfd" for consistency.
Second, the wording for the explanation of the arguments to the syscall
was a bit inconsistent, e.g. some used the past tense some used present
tense. Make the wording more consistent.

Signed-off-by: Christian Brauner

kernel/signal.c: trace_signal_deliver when signal_group_exit

2019-06-01T22:51:32+00:00

In the fixes commit, removing SIGKILL from each thread signal mask and
executing "goto fatal" directly will skip the call to
"trace_signal_deliver".  At this point, the delivery tracking of the
SIGKILL signal will be inaccurate.

Therefore, we need to add trace_signal_deliver before "goto fatal" after
executing sigdelset.

Note: SEND_SIG_NOINFO matches the fact that SIGKILL doesn't have any info.

Link: http://lkml.kernel.org/r/20190425025812.91424-1-weizhenliang@huawei.com
Fixes: cf43a757fd4944 ("signal: Restore the stop PTRACE_EVENT_EXIT")
Signed-off-by: Zhenliang Wei 
Reviewed-by: Christian Brauner 
Reviewed-by: Oleg Nesterov 
Cc: Eric W. Biederman 
Cc: Ivan Delalande 
Cc: Arnd Bergmann 
Cc: Thomas Gleixner 
Cc: Deepa Dinamani 
Cc: Greg Kroah-Hartman 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

signal: Remove the signal number and task parameters from force_sig_info

2019-05-29T14:31:44+00:00

force_sig_info always delivers to the current task and the signal
parameter always matches info.si_signo.  So remove those parameters to
make it a simpler less error prone interface, and to make it clear
that none of the callers are doing anything clever.

This guarantees that force_sig_info will not grow any new buggy
callers that attempt to call force_sig on a non-current task, or that
pass an signal number that does not match info.si_signo.

Signed-off-by: "Eric W. Biederman"

signal: Factor force_sig_info_to_task out of force_sig_info

2019-05-29T14:31:44+00:00

All callers of force_sig_info pass info.si_signo in for the signal
by definition as well as in practice.

Further all callers of force_sig_info except force_sig_fault_to_task
pass current as the target task to force_sig_info.

Factor out a static force_sig_info_to_task that
force_sig_fault_to_task can call.

This prepares the way for force_sig_info to have it's task and signal
parameters removed.

Signed-off-by: "Eric W. Biederman"