[PATCH 5.15 013/135] 9p: fix fid refcount leak in v9fs_vfs_get_link

[Greg Kroah-Hartman]

From: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>

commit e5690f263208c5abce7451370b7786eb25b405eb upstream.

we check for protocol version later than required, after a fid has
been obtained. Just move the version check earlier.

Link: https://lkml.kernel.org/r/20220612085330.1451496-3-asmadeus@xxxxxxxxxxxxx
Fixes: 6636b6dcc3db ("9p: add refcount to p9_fid struct")
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Christian Schoenebeck <linux_oss@xxxxxxxxxxxxx>
Signed-off-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/9p/vfs_inode.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -1228,15 +1228,15 @@ static const char *v9fs_vfs_get_link(str
 		return ERR_PTR(-ECHILD);
 
 	v9ses = v9fs_dentry2v9ses(dentry);
-	fid = v9fs_fid_lookup(dentry);
+	if (!v9fs_proto_dotu(v9ses))
+		return ERR_PTR(-EBADF);
+
 	p9_debug(P9_DEBUG_VFS, "%pd\n", dentry);
+	fid = v9fs_fid_lookup(dentry);
 
 	if (IS_ERR(fid))
 		return ERR_CAST(fid);
 
-	if (!v9fs_proto_dotu(v9ses))
-		return ERR_PTR(-EBADF);
-
 	st = p9_client_stat(fid);
 	p9_client_clunk(fid);
 	if (IS_ERR(st))