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commit a816fd6b49b6b0628b968faefd49a6de4ce27066
parent 4a3164e3d7be0e38a706f4345f418f2e31928332
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue,  2 Apr 2019 20:24:32 -1000

Merge tag 'pidfd-fixes-v5.1-rc3' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux

Pull pidfd fix from Christian Brauner:
 "This should be an uncontroversial fix for pidfd_send_signal() by Jann
  to better align it's behavior with other signal sending functions:

  In one of the early versions of the patchset it was suggested to not
  unconditionally error out when a signal with SI_USER is sent to a
  non-current task (cf. [1]).

  Instead, pidfd_send_signal() currently silently changes this to a
  regular kill signal. While this is technically fine, the semantics are
  weird since the kernel just silently converts a user's request behind
  their back and also no other signal sending function allows to do
  this. It gets more hairy when we introduce sending signals to a
  specific thread soon.

  So let's align pidfd_send_signal() with all the other signal sending
  functions and error out when SI_USER signals are sent to a non-current

* tag 'pidfd-fixes-v5.1-rc3' of gitolite.kernel.org:pub/scm/linux/kernel/git/brauner/linux:
  signal: don't silently convert SI_USER signals to non-current pidfd

Mkernel/signal.c | 13++++---------
1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c @@ -3605,16 +3605,11 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, if (unlikely(sig != kinfo.si_signo)) goto err; + /* Only allow sending arbitrary signals to yourself. */ + ret = -EPERM; if ((task_pid(current) != pid) && - (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)) { - /* Only allow sending arbitrary signals to yourself. */ - ret = -EPERM; - if (kinfo.si_code != SI_USER) - goto err; - - /* Turn this into a regular kill signal. */ - prepare_kill_siginfo(sig, &kinfo); - } + (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL)) + goto err; } else { prepare_kill_siginfo(sig, &kinfo); }