From: Jordy Zomer <jordy@pwning.systems>
Date: Wed, 17 Nov 2021 19:06:48 +0000 (+0100)
Subject: ipv6: check return value of ipv6_skip_exthdr
X-Git-Tag: v6.6.17~8780^2~4
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5f9c55c8066bcd93ac25234a02585701fe2e31df;p=platform%2Fkernel%2Flinux-rpi.git

ipv6: check return value of ipv6_skip_exthdr

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.

EDIT:  added {}'s, thanks Kees

Signed-off-by: Jordy Zomer <jordy@pwning.systems>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index ed2f061..f0bac6f 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -808,6 +808,12 @@ 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;
+		}
+
 		uh = (void *)(skb->data + offset);
 		th = (void *)(skb->data + offset);
 		hdr_len += offset;