ipv6: Fix out-of-bounds access in ipv6_find_tlv()

commit 878ecb0897f4737a4c9401f3523fd49589025671 upstream.

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: c61a40432509 ("[IPV6]: Find option offset by type.")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/exthdrs_core.c b/net/ipv6/exthdrs_core.c
index 305e2ed730bf42438190ad2fd7ae9ac9b4eed98f..d57d62efa6bdd75f07e63f6580b4ba8c4fd34eaa 100644 (file)
--- a/net/ipv6/exthdrs_core.c
+++ b/net/ipv6/exthdrs_core.c
@@ -142,6 +142,8 @@ 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;