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Date: Tue, 25 Jul 2023 12:01:33 +0200
From: Solar Designer <solar@...nwall.com>
To: oss-security@...ts.openwall.com
Subject: Re: CVE-2023-20593: A use-after-free in AMD Zen2 Processors
On Mon, Jul 24, 2023 at 07:28:18AM -0700, Tavis Ormandy wrote:
> Hello, this is CVE-2023-20593, a use-after-free in AMD Zen2 processors.
An impressive finding, indeed!
On a related note:
A few months earlier, Tavis found a _different_ AMD Zen1/Zen2 bug, which
turned out to have already been known and patched in AMD microcode
updates for many affected parts (but apparently not all). There's also
a kernel level workaround, which was included into Linux in response to
Tavis' rediscovery of that issue. Here are the links for that other
issue/fix, for distros to double-check they're fixing this one as well:
x86: AMD Zen2 ymm registers rolling back (Feb 21, 2023)
https://lore.kernel.org/lkml/Y%2FW4x7%2FKFqmDmmR7@thinkstation.cmpxchg8b.net/
x86/CPU/AMD: Disable XSAVES on AMD family 0x17 (Mar 8, 2023)
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b0563468eeac88ebc70559d52a0b66efc37e4e9d
Once again, it's a different bug - not the one that this oss-security
thread is mainly about - but both have cross-process security impact,
affect similar AMD CPUs, and need to be taken care of by similar means
(microcode updates or/and disabling of affected CPU features in the
kernel).
Alexander
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