[PATCH v2 07/16] fs/backing-file: Convert to cred_guard()

[Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>]

Replace the override_creds_light()/revert_creds_light() pairs of
operations to cred_guard().

For fs/backing-file.c, backing_file_open() and backing_tmpfile_open()
are not converted because they increase the usage counter of the
credentials in question.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
---
 fs/backing-file.c | 22 +++++-----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

diff --git a/fs/backing-file.c b/fs/backing-file.c
index bc19e8e28e58..29fe207a2032 100644
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -163,7 +163,6 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
 			       struct backing_file_ctx *ctx)
 {
 	struct backing_aio *aio = NULL;
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
@@ -176,7 +175,7 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
 	    !(file->f_mode & FMODE_CAN_ODIRECT))
 		return -EINVAL;
 
-	old_cred = override_creds_light(ctx->cred);
+	cred_guard(ctx->cred);
 	if (is_sync_kiocb(iocb)) {
 		rwf_t rwf = iocb_to_rw_flags(flags);
 
@@ -197,8 +196,6 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
 			backing_aio_cleanup(aio, ret);
 	}
 out:
-	revert_creds_light(old_cred);
-
 	if (ctx->accessed)
 		ctx->accessed(ctx->user_file);
 
@@ -210,7 +207,6 @@ ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
 				struct kiocb *iocb, int flags,
 				struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
@@ -233,7 +229,7 @@ ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
 	 */
 	flags &= ~IOCB_DIO_CALLER_COMP;
 
-	old_cred = override_creds_light(ctx->cred);
+	cred_guard(ctx->cred);
 	if (is_sync_kiocb(iocb)) {
 		rwf_t rwf = iocb_to_rw_flags(flags);
 
@@ -264,7 +260,6 @@ ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
 			backing_aio_cleanup(aio, ret);
 	}
 out:
-	revert_creds_light(old_cred);
 
 	return ret;
 }
@@ -275,15 +270,13 @@ ssize_t backing_file_splice_read(struct file *in, loff_t *ppos,
 				 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_light(ctx->cred);
+	cred_guard(ctx->cred);
 	ret = vfs_splice_read(in, ppos, pipe, len, flags);
-	revert_creds_light(old_cred);
 
 	if (ctx->accessed)
 		ctx->accessed(ctx->user_file);
@@ -297,7 +290,6 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 				  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)))
@@ -306,12 +298,10 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 	ret = file_remove_privs(ctx->user_file);
 	if (ret)
 		return ret;
-
-	old_cred = override_creds_light(ctx->cred);
+	cred_guard(ctx->cred);
 	file_start_write(out);
 	ret = iter_file_splice_write(pipe, out, ppos, len, flags);
 	file_end_write(out);
-	revert_creds_light(old_cred);
 
 	if (ctx->end_write)
 		ctx->end_write(ctx->user_file);
@@ -323,7 +313,6 @@ 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;
 	int ret;
 
 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)) ||
@@ -335,9 +324,8 @@ int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 
 	vma_set_file(vma, file);
 
-	old_cred = override_creds_light(ctx->cred);
+	cred_guard(ctx->cred);
 	ret = call_mmap(vma->vm_file, vma);
-	revert_creds_light(old_cred);
 
 	if (ctx->accessed)
 		ctx->accessed(ctx->user_file);
-- 
2.46.0