RE: CVE-2017-2615 Qemu: display: cirrus: oob access while doing bitblt copy backward mode

[李强 <liqiang6-s () 360 cn>]

Hello all,

This is Li Qiang from the Gear Team, Qihoo 360 inc. I have discovered this vulnerability and make a patch for this, 
though 
not complete. When I send patch to fix this issue, I did know the Cirrus vga is not the default vga in qemu. So I 
just treat this as a normal issue. But afterwards we discovered that the libvirt and xen use this vga as default.
We tested a lot of cloud platform in China, every of them uses the Cirrus vga as default. Most of them is affected by 
this
issue. The only one doesn't be affected I think have fixed this issue. So we think this issue should be got more 
attention. We 
strongly commend every cloud platform treat this issue seriously. Though this vulnerability has been fixed for 10+ days,
For responsible vulnerability disclosure, we will not public the PoC in this email. The PoC will be public later.

Thanks.

--
Li Qiang / the Gear Team, Qihoo 360 Inc.


> -----Original Message-----
> From: P J P [mailto:ppandit () redhat com]
> Sent: Wednesday, February 01, 2017 5:50 PM
> To: oss security list
> Cc: 李强
> Subject: CVE-2017-2615 Qemu: display: cirrus: oob access while doing bitblt
> copy backward mode
>
>    Hello,
>
> Quick emulator(Qemu) built with the Cirrus CLGD 54xx VGA Emulator support is
> vulnerable to an out-of-bounds access issue. It could occur while copying VGA
> data via bitblt copy in backward mode.
>
> A privileged user inside guest could use this flaw to crash the Qemu process
> resulting in DoS OR potentially execute arbitrary code on the host with
> privileges of Qemu process on the host.
>
> Upstream patch
> --------------
>    -> https://lists.gnu.org/archive/html/qemu-devel/2017-02/msg00015.html
>
> It fixes
>    ->
> http://git.qemu.org/?p=qemu.git;a=commit;h=d3532a0db02296e687711b8cdc
> 7791924efccea0
>
> Reference:
> ----------
>    -> https://bugzilla.redhat.com/show_bug.cgi?id=1418200
>
> This issue was reported by Li Qiang of 360.cn Inc.
>
> CVE-2017-2615 was assigned to this issue by Red Hat Inc.
>
> Thank you.
> --
> Prasad J Pandit / Red Hat Product Security Team 47AF CE69 3A90 54AA 9045
> 1053 DD13 3D32 FE5B 041F