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Re: [libvirt] [PATCH] command: avoid double close bugs



On 05/29/2012 09:51 PM, Wen Congyang wrote:
> At 05/30/2012 09:20 AM, Eric Blake Wrote:
>> KAMEZAWA Hiroyuki reported a nasty double-free bug when virCommand
>> is used to convert a string into input to a child command.  The
>> problem is that the poll() loop of virCommandProcessIO would close()
>> the write end of the pipe in order to let the child see EOF, then
>> the caller virCommandRun() would also close the same fd number, with
>> the second close possibly nuking an fd opened by some other thread
>> in the meantime.  This in turn can have all sorts of bad effects.
>>
>> This is based on his first attempt at a patch, at
>> https://bugzilla.redhat.com/show_bug.cgi?id=823716
> 
> close fd more twice is the cause of this bug. But there are some
> other codes that have the same problem. I am searching all such
> codes recent days.

Thanks for helping on that front.

>> +                    if (inoff == inlen && VIR_CLOSE(*inpipe) < 0)
>> +                        VIR_DEBUG("ignoring failed close on fd %d", infd);
>> +                    infd = -1;
> 
> if inoff != inlen, we should not set infd to -1.

Oh, good catch.  I'll post a v2.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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