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authorFlorian Westphal <fw@strlen.de>2018-02-19 01:24:15 +0100
committerPablo Neira Ayuso <pablo@netfilter.org>2018-02-25 20:07:33 +0100
commitb71812168571fa55e44cdd0254471331b9c4c4c6 (patch)
tree6dbae0f54e690041491407e6c0dee550fc67a60a /net
parentfc6a5d0601c5ac1d02f283a46f60b87b2033e5ca (diff)
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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>
Diffstat (limited to 'net')
-rw-r--r--net/bridge/netfilter/ebtables.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 61f87879e389..254ef9f49567 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/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;