Re: [Qemu-devel] [PATCH 06/17] block/nbd-client: fix nbd_read_reply_entry

[Eric Blake <eblake@redhat.com>]

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On 08/04/2017 10:14 AM, Vladimir Sementsov-Ogievskiy wrote:
> Set reply.handle to 0 on error path to prevent normal path of
> nbd_co_receive_reply.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  block/nbd-client.c | 1 +
>  1 file changed, 1 insertion(+)

Can you document a case where not fixing this would be an observable bug
(even if it requires using gdb and single-stepping between client and
server to make what is otherwise a racy situation easy to see)?  I'm
trying to figure out if this is 2.10 material.

> 
> diff --git a/block/nbd-client.c b/block/nbd-client.c
> index dc19894a7c..0c88d84de6 100644
> --- a/block/nbd-client.c
> +++ b/block/nbd-client.c
> @@ -107,6 +107,7 @@ static coroutine_fn void nbd_read_reply_entry(void *opaque)
>          qemu_coroutine_yield();
>      }
>  
> +    s->reply.handle = 0;
>      nbd_recv_coroutines_enter_all(s);
>      s->read_reply_co = NULL;
>  }
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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