net: handle no dst on skb in icmp6_send (CVE-2016-9919)

debian/changelog

@@ -51,6 +51,7 @@ linux (4.8.12-1) UNRELEASED; urgency=medium
   * Ignore ABI changes in KVM
   * net: ping: check minimum size on ICMP header length (CVE-2016-8399)
   * Don't feed anything but regular iovec's to blk_rq_map_user_iov (CVE-2016-9576)
+  * net: handle no dst on skb in icmp6_send (CVE-2016-9919)
 
   [ Ben Hutchings ]
   * [amd64] Re-enable LEGACY_VSYSCALL_EMULATE instead of LEGACY_VSYSCALL_NONE.

debian/patches/bugfix/all/net-handle-no-dst-on-skb-in-icmp6_send.patch

@@ -0,0 +1,71 @@
+From: David Ahern <dsa@cumulusnetworks.com>
+Date: Sun, 27 Nov 2016 18:52:53 -0800
+Subject: net: handle no dst on skb in icmp6_send
+Origin: https://git.kernel.org/linus/79dc7e3f1cd323be4c81aa1a94faa1b3ed987fb2
+
+Andrey reported the following while fuzzing the kernel with syzkaller:
+
+kasan: CONFIG_KASAN_INLINE enabled
+kasan: GPF could be caused by NULL-ptr deref or user memory access
+general protection fault: 0000 [#1] SMP KASAN
+Modules linked in:
+CPU: 0 PID: 3859 Comm: a.out Not tainted 4.9.0-rc6+ #429
+Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
+task: ffff8800666d4200 task.stack: ffff880067348000
+RIP: 0010:[<ffffffff833617ec>]  [<ffffffff833617ec>]
+icmp6_send+0x5fc/0x1e30 net/ipv6/icmp.c:451
+RSP: 0018:ffff88006734f2c0  EFLAGS: 00010206
+RAX: ffff8800666d4200 RBX: 0000000000000000 RCX: 0000000000000000
+RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 0000000000000018
+RBP: ffff88006734f630 R08: ffff880064138418 R09: 0000000000000003
+R10: dffffc0000000000 R11: 0000000000000005 R12: 0000000000000000
+R13: ffffffff84e7e200 R14: ffff880064138484 R15: ffff8800641383c0
+FS:  00007fb3887a07c0(0000) GS:ffff88006cc00000(0000) knlGS:0000000000000000
+CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+CR2: 0000000020000000 CR3: 000000006b040000 CR4: 00000000000006f0
+Stack:
+ ffff8800666d4200 ffff8800666d49f8 ffff8800666d4200 ffffffff84c02460
+ ffff8800666d4a1a 1ffff1000ccdaa2f ffff88006734f498 0000000000000046
+ ffff88006734f440 ffffffff832f4269 ffff880064ba7456 0000000000000000
+Call Trace:
+ [<ffffffff83364ddc>] icmpv6_param_prob+0x2c/0x40 net/ipv6/icmp.c:557
+ [<     inline     >] ip6_tlvopt_unknown net/ipv6/exthdrs.c:88
+ [<ffffffff83394405>] ip6_parse_tlv+0x555/0x670 net/ipv6/exthdrs.c:157
+ [<ffffffff8339a759>] ipv6_parse_hopopts+0x199/0x460 net/ipv6/exthdrs.c:663
+ [<ffffffff832ee773>] ipv6_rcv+0xfa3/0x1dc0 net/ipv6/ip6_input.c:191
+ ...
+
+icmp6_send / icmpv6_send is invoked for both rx and tx paths. In both
+cases the dst->dev should be preferred for determining the L3 domain
+if the dst has been set on the skb. Fallback to the skb->dev if it has
+not. This covers the case reported here where icmp6_send is invoked on
+Rx before the route lookup.
+
+Fixes: 5d41ce29e ("net: icmp6_send should use dst dev to determine L3 domain")
+Reported-by: Andrey Konovalov <andreyknvl@google.com>
+Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ net/ipv6/icmp.c | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
+index 7370ad2..2772004 100644
+--- a/net/ipv6/icmp.c
++++ b/net/ipv6/icmp.c
+@@ -447,8 +447,10 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
+ 
+ 	if (__ipv6_addr_needs_scope_id(addr_type))
+ 		iif = skb->dev->ifindex;
+-	else
+-		iif = l3mdev_master_ifindex(skb_dst(skb)->dev);
++	else {
++		dst = skb_dst(skb);
++		iif = l3mdev_master_ifindex(dst ? dst->dev : skb->dev);
++	}
+ 
+ 	/*
+ 	 *	Must not send error if the source does not uniquely
+-- 
+2.1.4
+

debian/patches/series

@@ -107,6 +107,7 @@ bugfix/all/packet-fix-race-condition-in-packet_set_ring.patch
 bugfix/all/net-avoid-signed-overflows-for-SO_-SND-RCV-BUFFORCE.patch
 bugfix/all/net-ping-check-minimum-size-on-ICMP-header-length.patch
 bugfix/all/Don-t-feed-anything-but-regular-iovec-s-to-blk_rq_ma.patch
+bugfix/all/net-handle-no-dst-on-skb-in-icmp6_send.patch
 
 # ABI maintenance