[PATCH] backing_file: Fix error code swallow

[Ethan Tidmore <ethantidmore06@gmail.com>]

The macro WARN_ON() returns true if the condition inside is true. So if
there is an error with vfs_open() 1 is returned.

Capture the return value of vfs_open() then run WARN_ON() on it.

Detected by Smatch:
fs/backing-file.c:52 backing_file_open() warn:
passing positive error code '1' to 'ERR_PTR'

fs/backing-file.c:77 backing_tmpfile_open() warn:
passing positive error code '1' to 'ERR_PTR'

Fixes: 7ea30795d6b7d ("backing_file: store user_path_file")
Signed-off-by: Ethan Tidmore <ethantidmore06@gmail.com>
---
 fs/file_table.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index e8b4eb2bbff8..0898b1816c14 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -69,8 +69,12 @@ EXPORT_SYMBOL_GPL(backing_file_user_path_file);
 
 int backing_file_open_user_path(struct file *f, const struct path *path)
 {
+	int ret;
+
 	/* open an O_PATH file to reference the user path - should not fail */
-	return WARN_ON(vfs_open(path, &backing_file(f)->user_path_file));
+	ret = vfs_open(path, &backing_file(f)->user_path_file);
+	WARN_ON(ret);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(backing_file_open_user_path);
 
-- 
2.53.0