[all-commits] [llvm/llvm-project] f17893: [libc] Fix chmod syscall arguments and add symlink...

[Pavel Labath via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f17893d88ac11a34fc26dacd78f18bde2836334b
      https://github.com/llvm/llvm-project/commit/f17893d88ac11a34fc26dacd78f18bde2836334b
  Author: Pavel Labath <pavel at labath.sk>
  Date:   2026-09-25 (Fri, 25 Sep 2026)

  Changed paths:
    M libc/src/__support/OSUtil/linux/syscall_wrappers/chmod.h
    M libc/src/sys/stat/linux/CMakeLists.txt
    M libc/test/src/sys/stat/CMakeLists.txt
    M libc/test/src/sys/stat/chmod_test.cpp

  Log Message:
  -----------
  [libc] Fix chmod syscall arguments and add symlink test (#226144)

Our Linux chmod wrapper had two bugs in how it invoked syscalls:
- the fchmodat syscall only takes three arguments (dfd, filename, mode),
but we were passing four (with a trailing 0 for flags).
- for fchmodat2, we were (mistakenly) passing AT_SYMLINK_NOFOLLOW, even
though chmod is specified to follow symlinks.

I reorder the checks to prefer fchmodat2 (with flags=0) if available,
and otherwise invoke fchmodat with the three arguments it expects.

I also add a test to verify that chmod follows symlinks and updates the
target file's permissions, and that attempting to chmod a dangling
symlink fails with ENOENT.

Assisted-by: Gemini



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