do_fchownat(): import pathname only once

Convert the user_path_at() call inside a retry loop into getname_flags() +
filename_lookup() + putname() and leave only filename_lookup() inside
the loop.

Since we have the default logics for use of LOOKUP_EMPTY (passed iff
AT_EMPTY_PATH is present in flags), just use getname_uflags() and
don't bother with setting LOOKUP_EMPTY in lookup_flags - getname_uflags()
will pass the right thing to getname_flags() and filename_lookup()
doesn't care about LOOKUP_EMPTY at all.

The things could be further simplified by use of cleanup.h stuff, but
let's not clutter the patch with that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/open.c b/fs/open.c
index 82bfa06dbfa54d104f68be906a74394138dbcfda..a2d775bec8c1d77e60e1d97499acd97bb33dfbaf 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -801,17 +801,17 @@ int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
                int flag)
 {
        struct path path;
-       int error = -EINVAL;
+       int error;
        int lookup_flags;
+       struct filename *name;
 
        if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
-               goto out;
+               return -EINVAL;
 
        lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
-       if (flag & AT_EMPTY_PATH)
-               lookup_flags |= LOOKUP_EMPTY;
+       name = getname_uflags(filename, flag);
 retry:
-       error = user_path_at(dfd, filename, lookup_flags, &path);
+       error = filename_lookup(dfd, name, lookup_flags, &path, NULL);
        if (error)
                goto out;
        error = mnt_want_write(path.mnt);
@@ -826,6 +826,7 @@ out_release:
                goto retry;
        }
 out:
+       putname(name);
        return error;
 }