blob: f40e6ec975d3814c1dbde9ac95bb7bbbfcf41558 [file] [log] [blame]
From 54970a2fbb673f090b7f02d7f57b10b2e0707155 Mon Sep 17 00:00:00 2001
From: Vasily Averin <vvs@virtuozzo.com>
Date: Mon, 14 Dec 2020 22:07:39 +0300
Subject: net: drop bogus skb with CHECKSUM_PARTIAL and offset beyond end of trimmed packet
From: Vasily Averin <vvs@virtuozzo.com>
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>
---
net/core/skbuff.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1592,6 +1592,12 @@ int pskb_trim_rcsum_slow(struct sk_buff
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);
}