On Tue, Sep 15, 2020 at 08:23:38PM -0400, Rich Felker wrote: > POSIX defines fchmodat as having a 4th argument, flags, that can be > AT_SYMLINK_NOFOLLOW. Support for changing the access mode of symbolic > links is optional (EOPNOTSUPP allowed if not supported), but this flag > is important even on systems where symlinks do not have access modes, > since it's the only way to safely change the mode of a file which > might be asynchronously replaced with a symbolic link, without a race > condition whereby the link target is changed. > > It's possible to emulate AT_SYMLINK_NOFOLLOW in userspace, and both > musl libc and glibc do this, by opening an O_PATH file descriptor and > performing chmod on the corresponding magic symlink in /proc/self/fd. > However, this requires procfs to be mounted and accessible. > > Signed-off-by: Rich Felker <dalias@xxxxxxxx> No kselftest for this new system call, or man page? How do we know this actually works and what the expected outcome should be? thanks, greg k-h
