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Subject[PATCH][next] ovl: fix null pointer dereference on null stack pointer on error return
Date
From: Colin Ian King <colin.king@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.king@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
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