Re: [Qemu-devel] [PATCH] nbd: Don't inf-loop on early EOF

[Paolo Bonzini <pbonzini@redhat.com>]

On 07/11/2016 23:45, Eric Blake wrote:
> On 11/07/2016 04:22 PM, Max Reitz wrote:
>> On 07.11.2016 21:38, Eric Blake wrote:
>>> Commit 7d3123e converted a single read_sync() into a while loop
>>> that assumed that read_sync() would either make progress or give
>>> an error. But when the server hangs up early, the client sees
>>> EOF (a read_sync() of 0) and never makes progress, which in turn
>>> caused qemu-iotest './check -nbd 83' to go into an infinite loop.
>>>
>>> Rework the loop to accomodate reads cut short by EOF.
>>>
>>> Reported-by: Max Reitz <mreitz@redhat.com>
>>> Signed-off-by: Eric Blake <eblake@redhat.com>
>>> ---
>>>  nbd/client.c | 13 +++++++------
>>>  1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> Reviewed-by: Max Reitz <mreitz@redhat.com>
>>
>> But what about the server's nbd_negotiate_drop_sync()? It uses pretty
>> much the same code, so it seems susceptible to the same issue (only that
>> we don't have a test for that side).
> 
> If so, that's an older bug (pre-existing back to at least 2.6?), so it
> should be a separate fix, if anything.
> 
> I guess it's time to figure out how to test the server against
> ill-behaved clients...

Using afl perhaps?

Paolo