[3.8.y.z extended stable] Patch "l2tp: fix kernel panic when using IPv4-mapped IPv6 addresses" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Fri Nov 1 21:43:37 UTC 2013


This is a note to let you know that I have just added a patch titled

    l2tp: fix kernel panic when using IPv4-mapped IPv6 addresses

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.13.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 9ccc0b07fc1a29e19cd64a9fdd60113ae31d8fbf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Cachereul?= <f.cachereul at alphalink.fr>
Date: Wed, 2 Oct 2013 10:16:02 +0200
Subject: l2tp: fix kernel panic when using IPv4-mapped IPv6 addresses
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

[ Upstream commit e18503f41f9b12132c95d7c31ca6ee5155e44e5c ]

IPv4 mapped addresses cause kernel panic.
The patch juste check whether the IPv6 address is an IPv4 mapped
address. If so, use IPv4 API instead of IPv6.

[  940.026915] general protection fault: 0000 [#1]
[  940.026915] Modules linked in: l2tp_ppp l2tp_netlink l2tp_core pppox ppp_generic slhc loop psmouse
[  940.026915] CPU: 0 PID: 3184 Comm: memcheck-amd64- Not tainted 3.11.0+ #1
[  940.026915] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[  940.026915] task: ffff880007130e20 ti: ffff88000737e000 task.ti: ffff88000737e000
[  940.026915] RIP: 0010:[<ffffffff81333780>]  [<ffffffff81333780>] ip6_xmit+0x276/0x326
[  940.026915] RSP: 0018:ffff88000737fd28  EFLAGS: 00010286
[  940.026915] RAX: c748521a75ceff48 RBX: ffff880000c30800 RCX: 0000000000000000
[  940.026915] RDX: ffff88000075cc4e RSI: 0000000000000028 RDI: ffff8800060e5a40
[  940.026915] RBP: ffff8800060e5a40 R08: 0000000000000000 R09: ffff88000075cc90
[  940.026915] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88000737fda0
[  940.026915] R13: 0000000000000000 R14: 0000000000002000 R15: ffff880005d3b580
[  940.026915] FS:  00007f163dc5e800(0000) GS:ffffffff81623000(0000) knlGS:0000000000000000
[  940.026915] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  940.026915] CR2: 00000004032dc940 CR3: 0000000005c25000 CR4: 00000000000006f0
[  940.026915] Stack:
[  940.026915]  ffff88000075cc4e ffffffff81694e90 ffff880000c30b38 0000000000000020
[  940.026915]  11000000523c4bac ffff88000737fdb4 0000000000000000 ffff880000c30800
[  940.026915]  ffff880005d3b580 ffff880000c30b38 ffff8800060e5a40 0000000000000020
[  940.026915] Call Trace:
[  940.026915]  [<ffffffff81356cc3>] ? inet6_csk_xmit+0xa4/0xc4
[  940.026915]  [<ffffffffa0038535>] ? l2tp_xmit_skb+0x503/0x55a [l2tp_core]
[  940.026915]  [<ffffffff812b8d3b>] ? pskb_expand_head+0x161/0x214
[  940.026915]  [<ffffffffa003e91d>] ? pppol2tp_xmit+0xf2/0x143 [l2tp_ppp]
[  940.026915]  [<ffffffffa00292e0>] ? ppp_channel_push+0x36/0x8b [ppp_generic]
[  940.026915]  [<ffffffffa00293fe>] ? ppp_write+0xaf/0xc5 [ppp_generic]
[  940.026915]  [<ffffffff8110ead4>] ? vfs_write+0xa2/0x106
[  940.026915]  [<ffffffff8110edd6>] ? SyS_write+0x56/0x8a
[  940.026915]  [<ffffffff81378ac0>] ? system_call_fastpath+0x16/0x1b
[  940.026915] Code: 00 49 8b 8f d8 00 00 00 66 83 7c 11 02 00 74 60 49
8b 47 58 48 83 e0 fe 48 8b 80 18 01 00 00 48 85 c0 74 13 48 8b 80 78 02
00 00 <48> ff 40 28 41 8b 57 68 48 01 50 30 48 8b 54 24 08 49 c7 c1 51
[  940.026915] RIP  [<ffffffff81333780>] ip6_xmit+0x276/0x326
[  940.026915]  RSP <ffff88000737fd28>
[  940.057945] ---[ end trace be8aba9a61c8b7f3 ]---
[  940.058583] Kernel panic - not syncing: Fatal exception in interrupt

Signed-off-by: Fran├žois CACHEREUL <f.cachereul at alphalink.fr>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/l2tp/l2tp_core.c | 27 +++++++++++++++++++++++----
 net/l2tp/l2tp_core.h |  3 +++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 2ac884d..8861e9f 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -517,6 +517,7 @@ out:
 static inline int l2tp_verify_udp_checksum(struct sock *sk,
 					   struct sk_buff *skb)
 {
+	struct l2tp_tunnel *tunnel = (struct l2tp_tunnel *)sk->sk_user_data;
 	struct udphdr *uh = udp_hdr(skb);
 	u16 ulen = ntohs(uh->len);
 	__wsum psum;
@@ -525,7 +526,7 @@ static inline int l2tp_verify_udp_checksum(struct sock *sk,
 		return 0;

 #if IS_ENABLED(CONFIG_IPV6)
-	if (sk->sk_family == PF_INET6) {
+	if (sk->sk_family == PF_INET6 && !tunnel->v4mapped) {
 		if (!uh->check) {
 			LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
 			return 1;
@@ -1088,7 +1089,7 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
 	/* Queue the packet to IP for output */
 	skb->local_df = 1;
 #if IS_ENABLED(CONFIG_IPV6)
-	if (skb->sk->sk_family == PF_INET6)
+	if (skb->sk->sk_family == PF_INET6 && !tunnel->v4mapped)
 		error = inet6_csk_xmit(skb, NULL);
 	else
 #endif
@@ -1221,7 +1222,7 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len

 		/* Calculate UDP checksum if configured to do so */
 #if IS_ENABLED(CONFIG_IPV6)
-		if (sk->sk_family == PF_INET6)
+		if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
 			l2tp_xmit_ipv6_csum(sk, skb, udp_len);
 		else
 #endif
@@ -1624,6 +1625,24 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
 	if (cfg != NULL)
 		tunnel->debug = cfg->debug;

+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == PF_INET6) {
+		struct ipv6_pinfo *np = inet6_sk(sk);
+
+		if (ipv6_addr_v4mapped(&np->saddr) &&
+		    ipv6_addr_v4mapped(&np->daddr)) {
+			struct inet_sock *inet = inet_sk(sk);
+
+			tunnel->v4mapped = true;
+			inet->inet_saddr = np->saddr.s6_addr32[3];
+			inet->inet_rcv_saddr = np->rcv_saddr.s6_addr32[3];
+			inet->inet_daddr = np->daddr.s6_addr32[3];
+		} else {
+			tunnel->v4mapped = false;
+		}
+	}
+#endif
+
 	/* Mark socket as an encapsulation socket. See net/ipv4/udp.c */
 	tunnel->encap = encap;
 	if (encap == L2TP_ENCAPTYPE_UDP) {
@@ -1631,7 +1650,7 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
 		udp_sk(sk)->encap_type = UDP_ENCAP_L2TPINUDP;
 		udp_sk(sk)->encap_rcv = l2tp_udp_encap_recv;
 #if IS_ENABLED(CONFIG_IPV6)
-		if (sk->sk_family == PF_INET6)
+		if (sk->sk_family == PF_INET6 && !tunnel->v4mapped)
 			udpv6_encap_enable();
 		else
 #endif
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index e62204c..8d6a048 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -190,6 +190,9 @@ struct l2tp_tunnel {
 	struct sock		*sock;		/* Parent socket */
 	int			fd;		/* Parent fd, if tunnel socket
 						 * was created by userspace */
+#if IS_ENABLED(CONFIG_IPV6)
+	bool			v4mapped;
+#endif

 	uint8_t			priv[0];	/* private data */
 };
--
1.8.1.2





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