Re: net/dccp: warning in dccp_set_state

[Andrey Konovalov]

Hi Eric,

I can confirm that with your patch the warning goes away.

Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

On Mon, Oct 24, 2016 at 2:52 PM, Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
> On Mon, 2016-10-24 at 05:47 -0700, Eric Dumazet wrote:
>> 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);
>>
>
> The equivalent tcp fix was :
> https://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=565b7b2d2e632b5792879c0c9cccdd9eecd31195
>
>