diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/fchmodat.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/fchmodat.c | 28 |
1 files changed, 24 insertions, 4 deletions
diff --git a/sysdeps/unix/sysv/linux/fchmodat.c b/sysdeps/unix/sysv/linux/fchmodat.c index 719053b333..17eca54051 100644 --- a/sysdeps/unix/sysv/linux/fchmodat.c +++ b/sysdeps/unix/sysv/linux/fchmodat.c @@ -45,6 +45,30 @@ fchmodat (int fd, const char *file, mode_t mode, int flag) caller can treat them as temporary if necessary. */ return pathfd; + /* Use fstatat because fstat does not work on O_PATH descriptors + before Linux 3.6. */ + struct stat64 st; + if (fstatat64 (pathfd, "", &st, AT_EMPTY_PATH) != 0) + { + __close_nocancel (pathfd); + return -1; + } + + /* Some Linux versions with some file systems can actually + change symbolic link permissions via /proc, but this is not + intentional, and it gives inconsistent results (e.g., error + return despite mode change). The expected behavior is that + symbolic link modes cannot be changed at all, and this check + enforces that. */ + if (S_ISLNK (st.st_mode)) + { + __close_nocancel (pathfd); + __set_errno (EOPNOTSUPP); + return -1; + } + + /* For most file systems, fchmod does not operate on O_PATH + descriptors, so go through /proc. */ char buf[32]; if (__snprintf (buf, sizeof (buf), "/proc/self/fd/%d", pathfd) < 0) { @@ -54,10 +78,6 @@ fchmodat (int fd, const char *file, mode_t mode, int flag) return -1; } - /* This operates directly on the symbolic link if it is one. - /proc/self/fd files look like symbolic links, but they are - not. (fchmod and fchmodat do not work on O_PATH descriptors, - similar to fstat before Linux 3.6.) */ int ret = __chmod (buf, mode); if (ret != 0) { |