netdev - [PATCH AUTOSEL 4.4 089/174] netfilter: ebtables: CONFIG_COMPAT: reject trailing data after last rule

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Message-Id: <20200116174251.24326-89-sashal@kernel.org>
Date:   Thu, 16 Jan 2020 12:41:26 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Florian Westphal <fw@...len.de>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Sasha Levin <sashal@...nel.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        bridge@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 089/174] netfilter: ebtables: CONFIG_COMPAT: reject trailing data after last rule

From: Florian Westphal <fw@...len.de>

[ Upstream commit 680f6af5337c98d116e4f127cea7845339dba8da ]

If userspace provides a rule blob with trailing data after last target,
we trigger a splat, then convert ruleset to 64bit format (with trailing
data), then pass that to do_replace_finish() which then returns -EINVAL.

Erroring out right away avoids the splat plus unneeded translation and
error unwind.

Fixes: 81e675c227ec ("netfilter: ebtables: add CONFIG_COMPAT support")
Reported-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 fd1af7cb960d..e7c170949b21 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2174,7 +2174,9 @@ static int compat_copy_entries(unsigned char *data, unsigned int size_user,
 	if (ret < 0)
 		return ret;
 
-	WARN_ON(size_remaining);
+	if (size_remaining)
+		return -EINVAL;
+
 	return state->buf_kern_offset;
 }
 
-- 
2.20.1