[PATCH][next] ovl: fix null pointer dereference on null stack pointer on error return

[Colin King]

From: Colin Ian King <colin.k...@canonical.com>

There are two error return paths where the call to path_put is
dereferencing the null pointer 'stack'.  Fix this by avoiding the
error exit path via label 'out_err' that will lead to the path_put
calls and instead just return the error code directly.

Addresses-Coverity: ("Dereference after null check)"
Fixes: 4155c10a0309 ("ovl: clean up getting lower layers")
Signed-off-by: Colin Ian King <colin.k...@canonical.com>
---
 fs/overlayfs/super.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 1094836f7e31..4be1b041b32c 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1594,20 +1594,18 @@ static struct ovl_entry *ovl_get_lowerstack(struct 
super_block *sb,
        unsigned int i;
        struct ovl_entry *oe;
 
-       err = -EINVAL;
        if (!ofs->config.upperdir && numlower == 1) {
                pr_err("at least 2 lowerdir are needed while upperdir 
nonexistent\n");
-               goto out_err;
+               return ERR_PTR(-EINVAL);
        } else if (!ofs->config.upperdir && ofs->config.nfs_export &&
                   ofs->config.redirect_follow) {
                pr_warn("NFS export requires \"redirect_dir=nofollow\" on 
non-upper mount, falling back to nfs_export=off.\n");
                ofs->config.nfs_export = false;
        }
 
-       err = -ENOMEM;
        stack = kcalloc(numlower, sizeof(struct path), GFP_KERNEL);
        if (!stack)
-               goto out_err;
+               return ERR_PTR(-ENOMEM);
 
        err = -EINVAL;
        for (i = 0; i < numlower; i++) {
-- 
2.25.1