netdev - [PATCH 07/16] backing-file: use credential guards for mmap

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Message-Id: <20251103-work-creds-guards-simple-v1-7-a3e156839e7f@kernel.org>
Date: Mon, 03 Nov 2025 12:26:55 +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 07/16] backing-file: use credential guards for mmap

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 | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/backing-file.c b/fs/backing-file.c
index 9c63a3368b66..5cc4b59aa460 100644
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -331,7 +331,6 @@ EXPORT_SYMBOL_GPL(backing_file_splice_write);
 int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 		      struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	struct file *user_file = vma->vm_file;
 	int ret;
 
@@ -343,9 +342,8 @@ int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 
 	vma_set_file(vma, file);
 
-	old_cred = override_creds(ctx->cred);
-	ret = vfs_mmap(vma->vm_file, vma);
-	revert_creds(old_cred);
+	scoped_with_creds(ctx->cred)
+		ret = vfs_mmap(vma->vm_file, vma);
 
 	if (ctx->accessed)
 		ctx->accessed(user_file);

-- 
2.47.3