fix failure of fchmodat to report EOPNOTSUPP in the race path

in the case where a non-symlink file was replaced by a symlink during
the fchmodat operation with AT_SYMLINK_NOFOLLOW, mode change on the
new symlink target was successfully suppressed, but the error was not
reported. instead, fchmodat simply returned 0.

(cherry picked from commit 61b1d102129990f6e903c6ddcf46c7d79d1a1e99)

(conflicts from commit dd5f50da6f6c3df5647e922e47f8568a8896a752)

diff --git a/src/stat/fchmodat.c b/src/stat/fchmodat.c
index 94d0335c06417e897efb662a9f798f2afbb24d7f..d94667aed5e1a4aa1e924bd89a8ba3aa3ec6aa16 100644 (file)
--- a/src/stat/fchmodat.c
+++ b/src/stat/fchmodat.c
@@ -28,8 +28,11 @@ int fchmodat(int fd, const char *path, mode_t mode, int flag)
        }
 
        __procfdname(proc, fd2);
-       if (!(ret = __syscall(SYS_stat, proc, &st)) && !S_ISLNK(st.st_mode))
-               ret = __syscall(SYS_chmod, proc, mode);
+       ret = __syscall(SYS_fstatat, AT_FDCWD, proc, &st, 0);
+       if (!ret) {
+               if (S_ISLNK(st.st_mode)) ret = -EOPNOTSUPP;
+               else ret = __syscall(SYS_fchmodat, AT_FDCWD, proc, mode);
+       }
 
        __syscall(SYS_close, fd2);
        return __syscall_ret(ret);