Re: [Qemu-devel] [PATCH] nbd: Fix regression on resiliency to port scan

[Eric Blake <eblake@redhat.com>]

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adding qemu-stable in cc

On 06/08/2017 05:26 PM, Eric Blake wrote:
> Back in qemu 2.5, qemu-nbd was immune to port probes (a transient
> server would not quit, regardless of how many probe connections
> came and went, until a connection actually negotiated).  But we
> broke that in commit ee7d7aa when removing the return value to
> nbd_client_new(), although that patch also introduced a bug causing
> an assertion failure on a client that fails negotiation.  We then
> made it worse during refactoring in commit 1a6245a (a segfault
> before we could even assert); the (masked) assertion was cleaned
> up in d3780c2 (still in 2.6), and just recently we finally fixed
> the segfault ("nbd: Fully intialize client in case of failed
> negotiation").  But that still means that ever since we added
> TLS support to qemu-nbd, we have been vulnerable to an ill-timed
> port-scan being able to cause a denial of service by taking down
> qemu-nbd before a real client has a chance to connect.
> 

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


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