Subject: Re: [PATCH] tipc: fix NULL pointer dereference in shutdown()

From: Vegard Nossum <[email-masked]>
Date: Fri, 12 Aug 2016 16:37:32 +0200

Hi,

I didn't see this patch go in yet. Jon Maloy, ping?

Should this go through somebody else?

Vegard

On 07/23/2016 11:49 AM, Xue, Ying wrote:
> Acked-by: Ying Xue <[email-masked]>
>
> -----Original Message-----
> From: Vegard Nossum [mailto:[email-masked]]
> Sent: Saturday, July 23, 2016 2:15 PM
> To: Jon Maloy; Xue, Ying
> Cc: [email-masked]; David S. Miller; Michael Kerrisk; [email-masked]; Vegard Nossum; [email-masked]
> Subject: [PATCH] tipc: fix NULL pointer dereference in shutdown()
>
> tipc_msg_create() can return a NULL skb and if so, we shouldn't try to call tipc_node_xmit_skb() on it.
>
>      general protection fault: 0000 [#1] PREEMPT SMP KASAN
>      CPU: 3 PID: 30298 Comm: trinity-c0 Not tainted 4.7.0-rc7+ #19
>      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
>      task: ffff8800baf09980 ti: ffff8800595b8000 task.ti: ffff8800595b8000
>      RIP: 0010:[<ffffffff830bb46b>]  [<ffffffff830bb46b>] tipc_node_xmit_skb+0x6b/0x140
>      RSP: 0018:ffff8800595bfce8  EFLAGS: 00010246
>      RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000003023b0e0
>      RDX: 0000000000000000 RSI: dffffc0000000000 RDI: ffffffff83d12580
>      RBP: ffff8800595bfd78 R08: ffffed000b2b7f32 R09: 0000000000000000
>      R10: fffffbfff0759725 R11: 0000000000000000 R12: 1ffff1000b2b7f9f
>      R13: ffff8800595bfd58 R14: ffffffff83d12580 R15: dffffc0000000000
>      FS:  00007fcdde242700(0000) GS:ffff88011af80000(0000) knlGS:0000000000000000
>      CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>      CR2: 00007fcddde1db10 CR3: 000000006874b000 CR4: 00000000000006e0
>      DR0: 00007fcdde248000 DR1: 00007fcddd73d000 DR2: 00007fcdde248000
>      DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000090602
>      Stack:
>       0000000000000018 0000000000000018 0000000041b58ab3 ffffffff83954208
>       ffffffff830bb400 ffff8800595bfd30 ffffffff8309d767 0000000000000018
>       0000000000000018 ffff8800595bfd78 ffffffff8309da1a 00000000810ee611
>      Call Trace:
>       [<ffffffff830c84a3>] tipc_shutdown+0x553/0x880
>       [<ffffffff825b4a3b>] SyS_shutdown+0x14b/0x170
>       [<ffffffff8100334c>] do_syscall_64+0x19c/0x410
>       [<ffffffff83295ca5>] entry_SYSCALL64_slow_path+0x25/0x25
>      Code: 90 00 b4 0b 83 c7 00 f1 f1 f1 f1 4c 8d 6d e0 c7 40 04 00 00 00 f4 c7 40 08 f3 f3 f3 f3 48 89 d8 48 c1 e8 03 c7 45 b4 00 00 00 00 <80> 3c 30 00 75 78 48 8d 7b 08 49 8d 75 c0 48 b8 00 00 00 00 00
>      RIP  [<ffffffff830bb46b>] tipc_node_xmit_skb+0x6b/0x140
>       RSP <ffff8800595bfce8>
>      ---[ end trace 57b0484e351e71f1 ]---
>
> I feel like we should maybe return -ENOMEM or -ENOBUFS, but I'm not sure userspace is equipped to handle that. Anyway, this is better than a GPF and looks somewhat consistent with other tipc_msg_create() callers.
>
> Cc: [email-masked]
> Signed-off-by: Vegard Nossum <[email-masked]>
> ---
>   net/tipc/socket.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/tipc/socket.c b/net/tipc/socket.c index c49b8df..f9f5f3c 100644
> --- a/net/tipc/socket.c
> +++ b/net/tipc/socket.c
> @@ -2180,7 +2180,8 @@ restart:
>   					      TIPC_CONN_MSG, SHORT_H_SIZE,
>   					      0, dnode, onode, dport, oport,
>   					      TIPC_CONN_SHUTDOWN);
> -			tipc_node_xmit_skb(net, skb, dnode, tsk->portid);
> +			if (skb)
> +				tipc_node_xmit_skb(net, skb, dnode, tsk->portid);
>   		}
>   		tsk->connected = 0;
>   		sock->state = SS_DISCONNECTING;
> --
> 1.9.1
>