Date: Mon, 25 Mar 2019 18:57:11 +0100 From: Solar Designer <solar@...nwall.com> To: john-users@...ts.openwall.com Subject: Re: can other user access secrets in GPU's memory? On Mon, Mar 25, 2019 at 08:10:58AM +0100, magnum wrote: > GPUs doesn't have any protection > against users reading your memory even *while* you're using it. In my > view is this is primarily a driver/runtime issue and ultimately even a > hardware issue (no memory protection in the design). Modern GPUs have MMUs, so the hardware is probably capable. I agree it's "primarily a driver/runtime issue". Also, I'm under impression NVIDIA cares about this issue already, but AMD doesn't care yet. We can try reporting this as a bug against the AMDGPU-PRO driver and see what happens. Aleksey, care to try? Also: On Mon, Mar 25, 2019 at 01:42:07AM +0300, Aleksey Cherepanov wrote: > I was playing around with OpenCL and it looks like memory is not zeroed > by default on GPUs, i.e. I can read old values from gpu on another run > of host program. So I guess it means that other users can read these > values too, right? Don't assume - actually test it as two different uses. While your guess is probably correct this time, it's conceivable for a driver to be smart and only zeroize memory before giving it to a different user, not to another OpenCL kernel invocation by the same user. So you need to test and make sure before reporting this as a bug. Thanks, Alexander
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