do_fchmodat(): 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 f3bacc583ef0137d84dd6844a853ae075091d6d8..82bfa06dbfa54d104f68be906a74394138dbcfda 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -679,6 +679,7 @@ static int do_fchmodat(int dfd, const char __user *filename, umode_t mode,
                       unsigned int flags)
 {
        struct path path;
+       struct filename *name;
        int error;
        unsigned int lookup_flags;
 
@@ -686,11 +687,9 @@ static int do_fchmodat(int dfd, const char __user *filename, umode_t mode,
                return -EINVAL;
 
        lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
-       if (flags & AT_EMPTY_PATH)
-               lookup_flags |= LOOKUP_EMPTY;
-
+       name = getname_uflags(filename, flags);
 retry:
-       error = user_path_at(dfd, filename, lookup_flags, &path);
+       error = filename_lookup(dfd, name, lookup_flags, &path, NULL);
        if (!error) {
                error = chmod_common(&path, mode);
                path_put(&path);
@@ -699,6 +698,7 @@ retry:
                        goto retry;
                }
        }
+       putname(name);
        return error;
 }