Commit 4a06fa67 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

ip: on queued skb use skb_header_pointer instead of pskb_may_pull 



Commit 2efd4fca ("ip: in cmsg IP(V6)_ORIGDSTADDR call
pskb_may_pull") avoided a read beyond the end of the skb linear
segment by calling pskb_may_pull.

That function can trigger a BUG_ON in pskb_expand_head if the skb is
shared, which it is when when peeking. It can also return ENOMEM.

Avoid both by switching to safer skb_header_pointer.

Fixes: 2efd4fca ("ip: in cmsg IP(V6)_ORIGDSTADDR call pskb_may_pull")
Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0b7959b6

net/ipv4/ip_sockglue.c

+5 −7
Original line number Diff line number Diff line
@@ -148,19 +148,17 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb) 


static void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb)

{

	__be16 _ports[2], *ports;

	struct sockaddr_in sin;

	__be16 *ports;

	int end;



	end = skb_transport_offset(skb) + 4;

	if (end > 0 && !pskb_may_pull(skb, end))

		return;



	/* All current transport protocols have the port numbers in the

	 * first four bytes of the transport header and this function is

	 * written with this assumption in mind.

	 */

	ports = (__be16 *)skb_transport_header(skb);

	ports = skb_header_pointer(skb, skb_transport_offset(skb),

				   sizeof(_ports), &_ports);

	if (!ports)

		return;



	sin.sin_family = AF_INET;

	sin.sin_addr.s_addr = ip_hdr(skb)->daddr;

net/ipv6/datagram.c

+4 −6
Original line number Diff line number Diff line
@@ -700,17 +700,15 @@ void ip6_datagram_recv_specific_ctl(struct sock *sk, struct msghdr *msg, 
	}

	if (np->rxopt.bits.rxorigdstaddr) {

		struct sockaddr_in6 sin6;

		__be16 *ports;

		int end;

		__be16 _ports[2], *ports;



		end = skb_transport_offset(skb) + 4;

		if (end <= 0 || pskb_may_pull(skb, end)) {

		ports = skb_header_pointer(skb, skb_transport_offset(skb),

					   sizeof(_ports), &_ports);

		if (ports) {

			/* All current transport protocols have the port numbers in the

			 * first four bytes of the transport header and this function is

			 * written with this assumption in mind.

			 */

			ports = (__be16 *)skb_transport_header(skb);



			sin6.sin6_family = AF_INET6;

			sin6.sin6_addr = ipv6_hdr(skb)->daddr;

			sin6.sin6_port = ports[1];

CRA Git | Maintained and supported by SUSTech CRA and CCSE