backing-file: use credential guards for splice read

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

Link: https://patch.msgid.link/20251103-work-creds-guards-simple-v1-5-a3e156839e7f@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/backing-file.c b/fs/backing-file.c
index 2ba0f3c..4d4edf9 100644 (file)
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -283,15 +283,13 @@ ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb,
                                 unsigned int flags,
                                 struct backing_file_ctx *ctx)
 {
-       const struct cred *old_cred;
        ssize_t ret;
 
        if (WARN_ON_ONCE(!(in->f_mode & FMODE_BACKING)))
                return -EIO;
 
-       old_cred = override_creds(ctx->cred);
-       ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags);
-       revert_creds(old_cred);
+       scoped_with_creds(ctx->cred)
+               ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags);
 
        if (ctx->accessed)
                ctx->accessed(iocb->ki_filp);