[PATCH 4.18 036/171] ovl: fix error handling in ovl_verify_set_fh()

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Amir Goldstein <amir73il@xxxxxxxxx>

commit babf4770be0adc69e6d2de150f4040f175e24beb upstream.

We hit a BUG on kfree of an ERR_PTR()...

Reported-by: syzbot+ff03fe05c717b82502d0@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 8b88a2e64036 ("ovl: verify upper root dir matches lower root dir")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.13
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/overlayfs/namei.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -441,8 +441,10 @@ int ovl_verify_set_fh(struct dentry *den
 
 	fh = ovl_encode_real_fh(real, is_upper);
 	err = PTR_ERR(fh);
-	if (IS_ERR(fh))
+	if (IS_ERR(fh)) {
+		fh = NULL;
 		goto fail;
+	}
 
 	err = ovl_verify_fh(dentry, name, fh);
 	if (set && err == -ENODATA)