linux-kernel - [PATCH] ovl: fix null pointer dereference on ofs allocation failure.

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Message-Id: <20171109174751.11683-1-colin.king@canonical.com>
Date:   Thu,  9 Nov 2017 17:47:51 +0000
From:   Colin King <colin.king@...onical.com>
To:     Miklos Szeredi <mszeredi@...hat.com>, linux-unionfs@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ovl: fix null pointer dereference on ofs allocation failure.

From: Colin Ian King <colin.king@...onical.com>

The current error exit path when ofs fails to allocate jumps
to clean-up code that calls ovl_free_fs resulting in a null pointer
dereference on the null ovl pointer.  Fix this by simply returning
with the -ENOMEM status in err.

Detected by CoverityScan, CID#1461284 ("Dereference after null check")

Fixes: 4f3bf9de9eac ("ovl: factor out ovl_free_fs() helper")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 fs/overlayfs/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 708afec913ac..8258a194695b 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1154,7 +1154,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 	err = -ENOMEM;
 	ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
 	if (!ofs)
-		goto out_err;
+		return err;

 	ofs->creator_cred = cred = prepare_creds();
 	if (!cred)
-- 
2.14.1