[PATCH AUTOSEL 4.9 137/251] netfilter: ebtables: CONFIG_COMPAT: reject trailing data after last rule

Sasha Levin
2020-01-16T17:39:51Z

From: Florian Westphal <fw@strlen.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@i-love.sakura.ne.jp>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 56b7197f0373..1d850edecd72 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2182,7 +2182,9 @@ 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