Commit 4522a70d authored by Jacob Wen's avatar Jacob Wen Committed by David S. Miller
Browse files

l2tp: fix reading optional fields of L2TPv3 



Use pskb_may_pull() to make sure the optional fields are in skb linear
parts, so we can safely read them later.

It's easy to reproduce the issue with a net driver that supports paged
skb data. Just create a L2TPv3 over IP tunnel and then generates some
network traffic.
Once reproduced, rx err in /sys/kernel/debug/l2tp/tunnels will increase.

Changes in v4:
1. s/l2tp_v3_pull_opt/l2tp_v3_ensure_opt_in_linear/
2. s/tunnel->version != L2TP_HDR_VER_2/tunnel->version == L2TP_HDR_VER_3/
3. Add 'Fixes' in commit messages.

Changes in v3:
1. To keep consistency, move the code out of l2tp_recv_common.
2. Use "net" instead of "net-next", since this is a bug fix.

Changes in v2:
1. Only fix L2TPv3 to make code simple.
   To fix both L2TPv3 and L2TPv2, we'd better refactor l2tp_recv_common.
   It's complicated to do so.
2. Reloading pointers after pskb_may_pull

Fixes: f7faffa3 ("l2tp: Add L2TPv3 protocol support")
Fixes: 0d76751f ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
Fixes: a32e0eec ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6")
Signed-off-by: default avatarJacob Wen <jian.w.wen@oracle.com>
Acked-by: default avatarGuillaume Nault <gnault@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3a03cb84

net/l2tp/l2tp_core.c

+4 −0
Original line number Diff line number Diff line
@@ -884,6 +884,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb) 
		goto error;

	}



	if (tunnel->version == L2TP_HDR_VER_3 &&

	    l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))

		goto error;



	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);

	l2tp_session_dec_refcount(session);

net/l2tp/l2tp_core.h

+20 −0
Original line number Diff line number Diff line
@@ -301,6 +301,26 @@ static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel) 
}

#endif



static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,

					       unsigned char **ptr, unsigned char **optr)

{

	int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);



	if (opt_len > 0) {

		int off = *ptr - *optr;



		if (!pskb_may_pull(skb, off + opt_len))

			return -1;



		if (skb->data != *optr) {

			*optr = skb->data;

			*ptr = skb->data + off;

		}

	}



	return 0;

}



#define l2tp_printk(ptr, type, func, fmt, ...)				\

do {									\

	if (((ptr)->debug) & (type))					\

net/l2tp/l2tp_ip.c

+3 −0
Original line number Diff line number Diff line
@@ -165,6 +165,9 @@ static int l2tp_ip_recv(struct sk_buff *skb) 
		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);

	}



	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))

		goto discard_sess;



	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);

	l2tp_session_dec_refcount(session);

net/l2tp/l2tp_ip6.c

+3 −0
Original line number Diff line number Diff line
@@ -178,6 +178,9 @@ static int l2tp_ip6_recv(struct sk_buff *skb) 
		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);

	}



	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))

		goto discard_sess;



	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);

	l2tp_session_dec_refcount(session);

CRA Git | Maintained and supported by SUSTech CRA and CCSE