Re: INFO: task hung in io_sq_thread_stop

[Jens Axboe <axboe@kernel.dk>]

On 9/9/20 4:03 AM, Stefano Garzarella wrote:
> On Wed, Sep 09, 2020 at 01:49:22AM -0700, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    dff9f829 Add linux-next specific files for 20200908
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=112f880d900000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=37b3426c77bda44c
>> dashboard link: https://syzkaller.appspot.com/bug?extid=3c23789ea938faaef049
>> compiler:       gcc (GCC) 10.1.0-syz 20200507
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17c082a5900000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1474f5f9900000
>>
>> Bisection is inconclusive: the first bad commit could be any of:
>>
>> d730b1a2 io_uring: add IOURING_REGISTER_RESTRICTIONS opcode
>> 7ec3d1dd io_uring: allow disabling rings during the creation
> 
> I'm not sure it is related, but while rebasing I forgot to update the
> right label in the error path.
> 
> Since the check of ring state is after the increase of ctx refcount, we
> need to decrease it jumping to 'out' label instead of 'out_fput':
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index d00eb6bf6ce9..f35da516095a 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8649,7 +8649,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
>                 goto out_fput;
> 
>         if (ctx->flags & IORING_SETUP_R_DISABLED)
> -               goto out_fput;
> +               goto out;
> 
>         /*
>          * For SQ polling, the thread will do all submissions and completions.
> 
> I'll send a patch ASAP and check if it solves this issue.

I think that's a separate bug, it's definitely a bug. So please do send
the fix, thanks.

-- 
Jens Axboe