From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Gross Subject: [PATCH 1/3] openvswitch: Add length check when retrieving TCP flags. Date: Mon, 7 May 2012 18:51:23 -0700 Message-ID: <1336441885-11085-2-git-send-email-jesse@nicira.com> References: <1336441885-11085-1-git-send-email-jesse@nicira.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Miller Return-path: In-Reply-To: <1336441885-11085-1-git-send-email-jesse-l0M0P4e3n4LQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org Errors-To: dev-bounces-yBygre7rU0TnMu66kgdUjQ@public.gmane.org List-Id: netdev.vger.kernel.org When collecting TCP flags we check that the IP header indicates that a TCP header is present but not that the packet is actually long enough to contain the header. This adds a check to prevent reading off the end of the packet. In practice, this is only likely to result in reading of bad data and not a crash due to the presence of struct skb_shared_info at the end of the packet. Signed-off-by: Jesse Gross --- net/openvswitch/flow.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c index 1252c30..2a11ec2 100644 --- a/net/openvswitch/flow.c +++ b/net/openvswitch/flow.c @@ -183,7 +183,8 @@ void ovs_flow_used(struct sw_flow *flow, struct sk_buff *skb) u8 tcp_flags = 0; if (flow->key.eth.type == htons(ETH_P_IP) && - flow->key.ip.proto == IPPROTO_TCP) { + flow->key.ip.proto == IPPROTO_TCP && + likely(skb->len >= skb_transport_offset(skb) + sizeof(struct tcphdr))) { u8 *tcp = (u8 *)tcp_hdr(skb); tcp_flags = *(tcp + TCP_FLAGS_OFFSET) & TCP_FLAG_MASK; } -- 1.7.9.5