linux-kernel - [PATCH 06/16] backing-file: use credential guards for splice write

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Message-Id: <20251103-work-creds-guards-simple-v1-6-a3e156839e7f@kernel.org>
Date: Mon, 03 Nov 2025 12:26:54 +0100
From: Christian Brauner <brauner@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-aio@...ck.org, linux-unionfs@...r.kernel.org, 
 linux-erofs@...ts.ozlabs.org, linux-nfs@...r.kernel.org, 
 linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org, 
 cgroups@...r.kernel.org, netdev@...r.kernel.org, 
 Christian Brauner <brauner@...nel.org>
Subject: [PATCH 06/16] backing-file: use credential guards for splice write

Use credential guards for scoped credential override with automatic
restoration on scope exit.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/backing-file.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/backing-file.c b/fs/backing-file.c
index 8ebc62f49bad..9c63a3368b66 100644
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -303,7 +303,6 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 				  size_t len, unsigned int flags,
 				  struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING)))
@@ -316,11 +315,11 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 	if (ret)
 		return ret;
 
-	old_cred = override_creds(ctx->cred);
-	file_start_write(out);
-	ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags);
-	file_end_write(out);
-	revert_creds(old_cred);
+	scoped_with_creds(ctx->cred) {
+		file_start_write(out);
+		ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags);
+		file_end_write(out);
+	}
 
 	if (ctx->end_write)
 		ctx->end_write(iocb, ret);

-- 
2.47.3