* chmod: fix TOCTOU race in recursive traversal
Use fchmodat2 (Linux 6.6+) with AT_SYMLINK_NOFOLLOW to prevent an
attacker from replacing a directory entry with a symlink between the
stat and chmod calls. Falls back to fchmodat on older kernels.
- Restrict fchmodat2 (syscall 452) to asm-generic architectures only
(x86_64, x86, arm, aarch64, riscv)
- Add SAFETY comment on unsafe syscall block per project convention
- Add O_PATH + /proc/self/fd fallback for musl on kernel < 6.6
- Cache ENOSYS result with AtomicBool to skip fchmodat2 on old kernels
- Remove unnecessary nix::Mode round-trip on the fchmodat2 path
- safe_chmod_file() takes explicit SymlinkBehavior parameter
- Always pass NoFollow for regular entries during recursion
- Document residual TOCTOU in symlink branch as intentional for -L
- Add test verifying NoFollow chmod doesn't modify symlink target
- Update check-safe-traversal.sh to recognize fchmodat2
`Mode::from_bits_truncate(DEST_INITIAL_MODE)` failed to build on macOS
because `mode_t` is `u16` there but `u32` on Linux. Compose the mode
from `Mode::RUSR | Mode::WUSR` so the call is portable by construction
and self-documents the intent (read+write owner = 0o600).
* factor: emit GNU's 'X is not a valid positive integer' wording
GNU's factor.c routes both stdin and command-line input through the same
print_factors() and reports invalid input as
factor: 'X' is not a valid positive integer
Match that wording exactly so the new GNU 9.11 'nul4' test passes and
the 'cont' test no longer needs the warning/invalid-digit hunk in
tests_factor_factor.pl.patch.
* Add 'cmdline' to spell-checker ignore list
Daniel Hofstetter
mattsu
oech3
Guillem L. Jara
xtqqczze
Dorian Péron
Sylvestre Ledru