diff options
| author | Vasily Averin <vvs@virtuozzo.com> | 2020-12-14 22:07:39 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-01-17 13:59:01 +0100 |
| commit | 8f9a69a92fc63917c9bd921b28e3b2912980becf (patch) | |
| tree | 86c59de02580e6a28f2821f60e35416c18b5068b | |
| parent | 45b5a900d51dadd5c269f2607db6dba97b70d3f7 (diff) | |
net: drop bogus skb with CHECKSUM_PARTIAL and offset beyond end of trimmed packet
commit 54970a2fbb673f090b7f02d7f57b10b2e0707155 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 c4f412526dfe..c062d340cd40 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1850,6 +1850,12 @@ 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); } |