Re: [Qemu-devel] Prevent overriding the input file with the output file when using qemu-img

[Eric Blake]

On 01/23/2018 08:48 AM, Eric Blake wrote:
> On 01/22/2018 10:40 PM, River Chiang wrote:
>>     Signed-off-by: River Chiang <address@hidden>
>>
>> ---------------------------------- qemu-img.c
>> ----------------------------------
>> index 68b375f998..5ce594ea00 100644
>> @@ -2098,6 +2098,9 @@ static int img_convert(int argc, char **argv)
>>      if (s.src_num < 1) {
>>          error_report("Must specify image file name");
>>          goto fail_getopt;
>> +    } else if (!strcmp(argv[optind], out_filename)) {
>> +        error_report("Override the input file with the output file");
>> +        goto fail_getopt;
> 
> Comparing names is too prone to false negatives.  'foo' and './foo' are
> the same file, but your test won't catch it.  Better might be checking
> if stat() reports the same dev/inode pair for the two files.
> 
> By the way, your patch is not in proper 'git send-email' format, which
> makes it hard to test whether it even applies.  More patch submission
> hints at http://wiki.qemu.org/Contribute/SubmitAPatch

Also, is this something that our image locking patches should be able
prevent automatically, without having to special case whether the
command line arguments refer to the same file, by the two different
command line arguments triggering conflicting locks?

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

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