[all-commits] [llvm/llvm-project] 23ead6: [compiler-rt][sanitizer_common] Fix setgroups sysc...

[Patrik Dokoupil via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 23ead65310da314ae04a1c30137f279beaac1a4f
      https://github.com/llvm/llvm-project/commit/23ead65310da314ae04a1c30137f279beaac1a4f
  Author: Patrik Dokoupil <61749375+pdokoupil at users.noreply.github.com>
  Date:   2026-07-15 (Wed, 15 Jul 2026)

  Changed paths:
    M compiler-rt/lib/sanitizer_common/sanitizer_common_syscalls.inc
    A compiler-rt/test/msan/Linux/syscalls_setgroups.cpp

  Log Message:
  -----------
  [compiler-rt][sanitizer_common] Fix setgroups syscall pre-hook to check its input (#209207)

# About

`PRE_SYSCALL(setgroups)`/`setgroups16` called `POST_WRITE` on their
`grouplist` argument, but grouplist is a read-only input the kernel
never writes. Under MSan, `POST_WRITE` maps to `__msan_unpoison`, so
annotating a raw setgroups(2) via the documented
`__sanitizer_syscall_pre_setgroups` hook silently marked an
uninitialized group list as initialized -- before the syscall even ran,
and even on failure -- masking a real use-of-uninitialized-value bug.
Under TSan it recorded a write range where a read belongs.

Use PRE_READ, matching every other input-only argument in this file
(e.g. sched_setparam). Add an MSan regression test.



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