Re: [Qemu-devel] [PATCH for-4.0-maybe] device_tree: Fix integer overflowing in load_device_tree()

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On Tue, 9 Apr 2019 at 21:15, Alistair Francis <address@hidden> wrote:
>>
>> On Tue, Apr 9, 2019 at 1:08 PM Peter Maydell <address@hidden> wrote:
>> >
>> > On Wed, 10 Apr 2019 at 00:40, Markus Armbruster <address@hidden> wrote:
>> > >
>> > > If the value of get_image_size() exceeds INT_MAX / 2 - 10000, the
>> > > computation of @dt_size overflows to a negative number, which then
>> > > gets converted to a very large size_t for g_malloc0() and
>> > > load_image_size().  In the (fortunately improbable) case g_malloc0()
>> > > succeeds and load_image_size() survives, we'd assign the negative
>> > > number to *sizep.  What that would do to the callers I can't say, but
>> > > it's unlikely to be good.
>> > >
>> > > Fix by rejecting images whose size would overflow.
>> > >
>> > > Signed-off-by: Markus Armbruster <address@hidden>
>> >
>> > I think this patch is missing some attributions for the
>> > security researchers who found the issue initially.
>> > PJP's patch for this from a couple of weeks back has a
>> > reported-by credit:
>> > https://patchew.org/QEMU/address@hidden/

Uh, I missed that thread.  Thanks for doing my homework for me!

>> It seems like from that discussion that this patch is the correct approach.
>>
>> I can add the attributions and send a PR for 4.0. I'll send it by EOD
>> unless anyone has any objections.
>
> Thanks. I think given it's 21:30 here I'm going to postpone
> tagging rc3 til tomorrow (mid-afternoon UK time). I'm still
> hoping we can avoid an rc4...

Want me to look for a few more integer overflows today?  ;-P