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Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges
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From: |
Eric Blake |
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Subject: |
Re: [Qemu-devel] [PATCH] xen_disk: convert discard input to byte ranges |
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Date: |
Tue, 22 Nov 2016 11:11:10 -0600 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 11/22/2016 11:00 AM, Olaf Hering wrote:
> On Tue, Nov 22, Eric Blake wrote:
>
>> if (sec_start + sec_count < sec_count ||
>> sec_start > (INT64_MAX >> BDRV_SECTOR_BITS) - sec_count) {
>> return false;
>> }
>
> My point was: how does this handle sec_start=0,sec_count=UINT64_MAX or
> sec_start=INT64_MAX,sec_count=INT64_MAX? For me this gets past the if().
Fair enough. Your test that things didn't overflow means that you can
then safely compare the sum to the limit, so go with:
if (sec_start + sec_count < sec_count ||
sec_start + sec_count > INT64_MAX >> BDRV_SECTOR_BITS) {
return false;
}
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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