ovl: Fix kernel panic while mounting overlayfs

The function ovl_fill_super() in recently multi-layer support
version will incorrectly return 0 at error handling path and
then cause kernel panic.

This failure can be reproduced by mounting a overlayfs with
upperdir and workdir in different mounts.

And also, If the memory allocation of *lower_mnt* fail, this
function may return an zero either.

This patch fix this problem by setting *err* to proper error
number before jumping to error handling path.

Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 84f3144e1b33..6ca8ea8cb9b2 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -836,6 +836,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                 if (err)
                         goto out_put_upperpath;
 
+                err = -EINVAL;
                 if (upperpath.mnt != workpath.mnt) {
                         pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
                         goto out_put_workpath;
@@ -894,12 +895,14 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
                 }
         }
 
+        err = -ENOMEM;
         ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
         if (ufs->lower_mnt == NULL)
                 goto out_put_workdir;
         for (i = 0; i < numlower; i++) {
                 struct vfsmount *mnt = clone_private_mount(&stack[i]);
 
+                err = PTR_ERR(mnt);
                 if (IS_ERR(mnt)) {
                         pr_err("overlayfs: failed to clone lowerpath\n");
                         goto out_put_lower_mnt;