linux-kernel - [RFC PATCH v3 08/59] do_sys_truncate(): import pathname only once

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Message-ID: <20251216035518.4037331-9-viro@zeniv.linux.org.uk>
Date: Tue, 16 Dec 2025 03:54:27 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: linux-fsdevel@...r.kernel.org
Cc: torvalds@...ux-foundation.org,
	brauner@...nel.org,
	jack@...e.cz,
	mjguzik@...il.com,
	paul@...l-moore.com,
	axboe@...nel.dk,
	audit@...r.kernel.org,
	io-uring@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH v3 08/59] do_sys_truncate(): 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.

In this case we never pass LOOKUP_EMPTY, so getname_flags() is equivalent
to plain getname().

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@...iv.linux.org.uk>
---
 fs/open.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/open.c b/fs/open.c
index 6f48fa9c756a..2fea68991d42 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -129,14 +129,16 @@ EXPORT_SYMBOL_GPL(vfs_truncate);
 int do_sys_truncate(const char __user *pathname, loff_t length)
 {
 	unsigned int lookup_flags = LOOKUP_FOLLOW;
+	struct filename *name;
 	struct path path;
 	int error;
 
 	if (length < 0)	/* sorry, but loff_t says... */
 		return -EINVAL;
 
+	name = getname(pathname);
 retry:
-	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
+	error = filename_lookup(AT_FDCWD, name, lookup_flags, &path, NULL);
 	if (!error) {
 		error = vfs_truncate(&path, length);
 		path_put(&path);
@@ -145,6 +147,7 @@ int do_sys_truncate(const char __user *pathname, loff_t length)
 		lookup_flags |= LOOKUP_REVAL;
 		goto retry;
 	}
+	putname(name);
 	return error;
 }
 
-- 
2.47.3