From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 1 Nov 2025 04:48:31 +0000 (-0400)
Subject: do_fchmodat(): import pathname only once
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=67591df968f4ceb12c1f5d7f9caebc668200856b;p=thirdparty%2Fkernel%2Flinux.git

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 f3bacc583ef01..82bfa06dbfa54 100644
--- 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;
 }