diff options
| author | Vasily Averin <vvs@virtuozzo.com> | 2020-12-14 22:07:39 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2020-12-14 18:41:01 -0800 |
| commit | 54970a2fbb673f090b7f02d7f57b10b2e0707155 (patch) | |
| tree | 11b28387872b78f796c1f7402261cd4fd960f963 /net | |
| parent | 0780b4145634c3e8d69905dc5d2695d1207130df (diff) | |
| download | linux-54970a2fbb673f090b7f02d7f57b10b2e0707155.tar.bz2 | |
net: drop bogus skb with CHECKSUM_PARTIAL and offset beyond end of trimmed packet
syzbot reproduces BUG_ON in skb_checksum_help():
tun creates (bogus) skb with huge partial-checksummed area and
small ip packet inside. Then ip_rcv trims the skb based on size
of internal ip packet, after that csum offset points beyond of
trimmed skb. Then checksum_tg() called via netfilter hook
triggers BUG_ON:
offset = skb_checksum_start_offset(skb);
BUG_ON(offset >= skb_headlen(skb));
To work around the problem this patch forces pskb_trim_rcsum_slow()
to return -EINVAL in described scenario. It allows its callers to
drop such kind of packets.
Link: https://syzkaller.appspot.com/bug?id=b419a5ca95062664fe1a60b764621eb4526e2cd0
Reported-by: syzbot+7010af67ced6105e5ab6@syzkaller.appspotmail.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/1b2494af-2c56-8ee2-7bc0-923fcad1cdf8@virtuozzo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/skbuff.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index bfa5c9969393..f62cae3f75d8 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2018,6 +2018,12 @@ int pskb_trim_rcsum_slow(struct sk_buff *skb, unsigned int len) skb->csum = csum_block_sub(skb->csum, skb_checksum(skb, len, delta, 0), len); + } else if (skb->ip_summed == CHECKSUM_PARTIAL) { + int hdlen = (len > skb_headlen(skb)) ? skb_headlen(skb) : len; + int offset = skb_checksum_start_offset(skb) + skb->csum_offset; + + if (offset + sizeof(__sum16) > hdlen) + return -EINVAL; } return __pskb_trim(skb, len); } |