This is a note to let you know that I've just added the patch titled

netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: netfilter-ebtables-config_compat-don-t-trust-userland-offsets.patch and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From b71812168571fa55e44cdd0254471331b9c4c4c6 Mon Sep 17 00:00:00 2001

From: Florian Westphal fw@strlen.de Date: Mon, 19 Feb 2018 01:24:15 +0100 Subject: netfilter: ebtables: CONFIG_COMPAT: don't trust userland offsets

From: Florian Westphal fw@strlen.de

commit b71812168571fa55e44cdd0254471331b9c4c4c6 upstream.

We need to make sure the offsets are not out of range of the total size. Also check that they are in ascending order.

The WARN_ON triggered by syzkaller (it sets panic_on_warn) is changed to also bail out, no point in continuing parsing.

Briefly tested with simple ruleset of -A INPUT --limit 1/s' --log plus jump to custom chains using 32bit ebtables binary.

Reported-by: syzbot+845a53d13171abf8bf29@syzkaller.appspotmail.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- net/bridge/netfilter/ebtables.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/net/bridge/netfilter/ebtables.c +++ b/net/bridge/netfilter/ebtables.c @@ -2019,7 +2019,9 @@ static int ebt_size_mwt(struct compat_eb if (match_kern) match_kern->match_size = ret;

- WARN_ON(type == EBT_COMPAT_TARGET && size_left); + if (WARN_ON(type == EBT_COMPAT_TARGET && size_left)) + return -EINVAL; + match32 = (struct compat_ebt_entry_mwt *) buf; }

@@ -2076,6 +2078,15 @@ static int size_entry_mwt(struct ebt_ent * * offsets are relative to beginning of struct ebt_entry (i.e., 0). */ + for (i = 0; i < 4 ; ++i) { + if (offsets[i] >= *total) + return -EINVAL; + if (i == 0) + continue; + if (offsets[i-1] > offsets[i]) + return -EINVAL; + } + for (i = 0, j = 1 ; j < 4 ; j++, i++) { struct compat_ebt_entry_mwt *match32; unsigned int size;

Patches currently in stable-queue which might be from fw@strlen.de are

queue-3.18/netfilter-ipv6-fix-use-after-free-write-in-nf_nat_ipv6_manip_pkt.patch queue-3.18/netfilter-ebtables-config_compat-don-t-trust-userland-offsets.patch queue-3.18/netfilter-bridge-ebt_among-add-missing-match-size-checks.patch