Re: [PATCH] hw/core/loader: Fix possible crash in rom_copy()

[Thomas Huth <thuth@redhat.com>]

On 25/09/2019 22.51, Philippe Mathieu-Daudé wrote:
> Hi Thomas,
> 
> On 9/25/19 3:03 PM, Thomas Huth wrote:
>> Both, "rom->addr" and "addr" are derived from the binary image
>> that can be loaded with the "-kernel" paramer. The code in
>> rom_copy() then calculates:
>>
>>     d = dest + (rom->addr - addr);
>>
>> and uses "d" as destination in a memcpy() some lines later. Now with
>> bad kernel images, it is possible that rom->addr is smaller than addr,
>> thus "rom->addr - addr" gets negative and the memcpy() then tries to
>> copy contents from the image to a bad memory location. In the best case,
>> this just crashes QEMU, in the worst case, this could maybe be used to
>> inject code from the kernel image into the QEMU binary, so we better fix
>> it with an additional sanity check here.
>>
>> Cc: qemu-stable@nongnu.org
>> Reported-by: Guangming Liu
>> Buglink: https://bugs.launchpad.net/qemu/+bug/1844635
> 
> "This page does not exist, or you may not have permission to see it."
> 
> This seems security related. Shouldn't we open a CVE for this?
> https://wiki.qemu.org/SecurityProcess#CVE_allocation

I wrote to the security team before writing the patch, so I assume a CVE
number is already on the way. I'll reply to this thread when it is
available.

 Thomas