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From:   Wenwen Wang <wang6495@umn.edu>
To:     Wenwen Wang <wenwen@cs.uga.edu>
Cc:     Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@netfilter.org>,
        Florian Westphal <fw@strlen.de>,
        Roopa Prabhu <roopa@cumulusnetworks.com>,
        Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
        "David S. Miller" <davem@davemloft.net>,
        netfilter-devel@vger.kernel.org (open list:NETFILTER),
        coreteam@netfilter.org (open list:NETFILTER),
        bridge@lists.linux-foundation.org (moderated list:ETHERNET BRIDGE),
        netdev@vger.kernel.org (open list:ETHERNET BRIDGE),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH] netfilter: ebtables: compat: fix a memory leak bug
Date:   Sat, 20 Jul 2019 07:22:45 -0500
Message-Id: <1563625366-3602-1-git-send-email-wang6495@umn.edu>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Wenwen Wang <wenwen@cs.uga.edu>

In compat_do_replace(), a temporary buffer is allocated through vmalloc()
to hold entries copied from the user space. The buffer address is firstly
saved to 'newinfo->entries', and later on assigned to 'entries_tmp'. Then
the entries in this temporary buffer is copied to the internal kernel
structure through compat_copy_entries(). If this copy process fails,
compat_do_replace() should be terminated. However, the allocated temporary
buffer is not freed on this path, leading to a memory leak.

To fix the bug, free the buffer before returning from compat_do_replace().

Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
---
 net/bridge/netfilter/ebtables.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 963dfdc..fd84b48e 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2261,8 +2261,10 @@ static int compat_do_replace(struct net *net, void __user *user,
 	state.buf_kern_len = size64;
 
 	ret = compat_copy_entries(entries_tmp, tmp.entries_size, &state);
-	if (WARN_ON(ret < 0))
+	if (WARN_ON(ret < 0)) {
+		vfree(entries_tmp);
 		goto out_unlock;
+	}
 
 	vfree(entries_tmp);
 	tmp.entries_size = size64;
-- 
2.7.4