[PATCH net] ipv6: Fix out-of-bounds access in ipv6_find_tlv()

[Gavrilov Ilia]

optlen is fetched without checking whether there is more than one byte to parse.
It can lead to out-of-bounds access.

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: 3c73a0368e99 ("ipv6: Update ipv6 static library with newly needed functions")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
---
 net/ipv6/exthdrs_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv6/exthdrs_core.c b/net/ipv6/exthdrs_core.c
index da46c4284676..49e31e4ae7b7 100644
--- a/net/ipv6/exthdrs_core.c
+++ b/net/ipv6/exthdrs_core.c
@@ -143,6 +143,8 @@ int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type)
 			optlen = 1;
 			break;
 		default:
+			if (len < 2)
+				goto bad;
 			optlen = nh[offset + 1] + 2;
 			if (optlen > len)
 				goto bad;
-- 
2.30.2