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Mickaël Salaün c5efa393d8
selftests/landlock: Add a new test for setuid()
The new signal_scoping_thread_setuid tests check that the libc's
setuid() function works as expected even when a thread is sandboxed with
scoped signal restrictions.

Before the signal scoping fix, this test would have failed with the
setuid() call:

  [pid    65] getpid()                    = 65
  [pid    65] tgkill(65, 66, SIGRT_1)     = -1 EPERM (Operation not permitted)
  [pid    65] futex(0x40a66cdc, FUTEX_WAKE_PRIVATE, 1) = 0
  [pid    65] setuid(1001)                = 0

After the fix, tgkill(2) is successfully leveraged to synchronize
credentials update across threads:

  [pid    65] getpid()                    = 65
  [pid    65] tgkill(65, 66, SIGRT_1)     = 0
  [pid    66] <... read resumed>0x40a65eb7, 1) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
  [pid    66] --- SIGRT_1 {si_signo=SIGRT_1, si_code=SI_TKILL, si_pid=65, si_uid=1000} ---
  [pid    66] getpid()                    = 65
  [pid    66] setuid(1001)                = 0
  [pid    66] futex(0x40a66cdc, FUTEX_WAKE_PRIVATE, 1) = 0
  [pid    66] rt_sigreturn({mask=[]})     = 0
  [pid    66] read(3,  <unfinished ...>
  [pid    65] setuid(1001)                = 0

Test coverage for security/landlock is 92.9% of 1137 lines according to
gcc/gcov-14.

Fixes: c899496501 ("selftests/landlock: Test signal scoping for threads")
Cc: Günther Noack <gnoack@google.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250318161443.279194-8-mic@digikod.net
[mic: Update test coverage]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
History 2025-03-26 13:59:32 +01:00
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Linux kernel
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There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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Please read the Documentation/process/changes.rst file, as it contains the
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