[PATCH nf] netfilter: ebtables: CONFIG_COMPAT: reject trailing data after last rule

[PATCH nf] netfilter: ebtables: CONFIG_COMPAT: reject trailing data after last rule

[Florian Westphal]

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>
---
 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 3cad01ac64e4..3a1b94b5c0e5 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -2158,7 +2158,9 @@ 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

Re: [PATCH nf] netfilter: ebtables: CONFIG_COMPAT: reject trailing data after last rule

[Pablo Neira Ayuso]

On Sun, May 05, 2019 at 06:47:33PM +0200, Florian Westphal wrote:
> 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,

Applied, thanks Florian.