ACK: [CVE-2016-9919][yakkety] net: handle no dst on skb in icmp6_send

Luis Henriques luis.henriques at canonical.com
Mon Dec 12 16:05:40 UTC 2016


On Mon, Dec 12, 2016 at 01:59:25PM -0200, Thadeu Lima de Souza Cascardo wrote:
> From: David Ahern <dsa at cumulusnetworks.com>
> 
> BugLink: https://launchpad.net/bugs/1648662
> 
> 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 at google.com>
> Signed-off-by: David Ahern <dsa at cumulusnetworks.com>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry picked from commit 79dc7e3f1cd323be4c81aa1a94faa1b3ed987fb2)
> CVE-2016-9919
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
> ---
>  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
> -- 
> 2.9.3
> 
> 
> -- 
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
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Cheers,
--
Luís
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