Re: net/dccp: warning in dccp_set_state

[Eric Dumazet]

On Mon, 2016-10-24 at 14:23 +0200, Andrey Konovalov wrote:
> Hi,
> 
> I've got the following error report while running the syzkaller fuzzer:
> 
> WARNING: CPU: 1 PID: 21072 at net/dccp/proto.c:83 dccp_set_state+0x229/0x290
> Kernel panic - not syncing: panic_on_warn set ...
> 
> CPU: 1 PID: 21072 Comm: syz-executor Not tainted 4.9.0-rc1+ #293
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  ffff88003d4c7738 ffffffff81b474f4 0000000000000003 dffffc0000000000
>  ffffffff844f8b00 ffff88003d4c7804 ffff88003d4c7800 ffffffff8140c06a
>  0000000041b58ab3 ffffffff8479ab7d ffffffff8140beae ffffffff8140cd00
> Call Trace:
>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>  [<ffffffff81b474f4>] dump_stack+0xb3/0x10f lib/dump_stack.c:51
>  [<ffffffff8140c06a>] panic+0x1bc/0x39d kernel/panic.c:179
>  [<ffffffff8111125c>] __warn+0x1cc/0x1f0 kernel/panic.c:542
>  [<ffffffff8111144c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
>  [<ffffffff8389e5d9>] dccp_set_state+0x229/0x290 net/dccp/proto.c:83
>  [<ffffffff838a0aa2>] dccp_close+0x612/0xc10 net/dccp/proto.c:1016
>  [<ffffffff8316bf1f>] inet_release+0xef/0x1c0 net/ipv4/af_inet.c:415
>  [<ffffffff82b6e89e>] sock_release+0x8e/0x1d0 net/socket.c:570
>  [<ffffffff82b6e9f6>] sock_close+0x16/0x20 net/socket.c:1017
>  [<ffffffff815256ad>] __fput+0x29d/0x720 fs/file_table.c:208
>  [<ffffffff81525bb5>] ____fput+0x15/0x20 fs/file_table.c:244
>  [<ffffffff811727d8>] task_work_run+0xf8/0x170 kernel/task_work.c:116
>  [<     inline     >] exit_task_work include/linux/task_work.h:21
>  [<ffffffff8111bc53>] do_exit+0x883/0x2ac0 kernel/exit.c:828
>  [<ffffffff811221fe>] do_group_exit+0x10e/0x340 kernel/exit.c:931
>  [<ffffffff81143c94>] get_signal+0x634/0x15a0 kernel/signal.c:2307
>  [<ffffffff81054aad>] do_signal+0x8d/0x1a30 arch/x86/kernel/signal.c:807
>  [<ffffffff81003a05>] exit_to_usermode_loop+0xe5/0x130
> arch/x86/entry/common.c:156
>  [<     inline     >] prepare_exit_to_usermode arch/x86/entry/common.c:190
>  [<ffffffff81006298>] syscall_return_slowpath+0x1a8/0x1e0
> arch/x86/entry/common.c:259
>  [<ffffffff83fc1a62>] entry_SYSCALL_64_fastpath+0xc0/0xc2
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> 
> On commit 1a1891d762d6e64daf07b5be4817e3fbb29e3c59 (Oct 18).

Not sure we we keep around DCCP. David could we kill it ?

TCP seems to have an additional check, missing in DCCP.

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index 41e65804ddf5..9fe25bf63296 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1009,6 +1009,10 @@ void dccp_close(struct sock *sk, long timeout)
 		__kfree_skb(skb);
 	}
 
+	/* If socket has been already reset kill it. */
+	if (sk->sk_state == DCCP_CLOSED)
+		goto adjudge_to_death;
+
 	if (data_was_unread) {
 		/* Unread data was tossed, send an appropriate Reset Code */
 		DCCP_WARN("ABORT with %u bytes unread\n", data_was_unread);