Re: [PATCH] ipv6: check return value of ipv6_skip_exthdr
From: Kees Cook <hidden>
Date: 2021-11-17 18:46:39
Also in:
linux-hardening, lkml
On Wed, Nov 17, 2021 at 07:16:10PM +0100, Jordy Zomer wrote:
quoted hunk ↗ jump to hunk
The offset value is used in pointer math on skb->data. Since ipv6_skip_exthdr may return -1 the pointer to uh and th may not point to the actual udp and tcp headers and potentially overwrite other stuff. This is why I think this should be checked. Signed-off-by: Jordy Zomer <redacted> --- net/ipv6/esp6.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c index ed2f061b8768..dc4251655df9 100644 --- a/net/ipv6/esp6.c +++ b/net/ipv6/esp6.c@@ -808,6 +808,11 @@ int esp6_input_done2(struct sk_buff *skb, int err) struct tcphdr *th; offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off); + + if (offset < 0) + err = -EINVAL; + goto out; +
Oh, and, this needs { }s. The CI noticed too:
https://patchwork.kernel.org/project/netdevbpf/patch/20211117181610.2731938-1-jordy@pwning.systems/
uh = (void *)(skb->data + offset); th = (void *)(skb->data + offset); hdr_len += offset; -- 2.27.0
-- Kees Cook