Skip to content
Permalink
Browse files

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

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>
  • Loading branch information...
Florian Westphal authored and ummakynes committed Feb 19, 2018
1 parent fc6a5d0 commit b71812168571fa55e44cdd0254471331b9c4c4c6
Showing with 12 additions and 1 deletion.
  1. +12 −1 net/bridge/netfilter/ebtables.c
@@ -2060,7 +2060,9 @@ static int ebt_size_mwt(struct compat_ebt_entry_mwt *match32,
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;
}

@@ -2116,6 +2118,15 @@ static int size_entry_mwt(struct ebt_entry *entry, const unsigned char *base,
*
* 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;

0 comments on commit b718121

Please sign in to comment.
You can’t perform that action at this time.