From: Dave Hansen <dave.hansen@intel.com>
To: Jim Mattson <jmattson@google.com>,
linux-kernel@vger.kernel.org, x86@kernel.org
Cc: Tavis Ormandy <taviso@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Kyle Huey <me@kylehuey.com>,
"Chang S. Bae" <chang.seok.bae@intel.com>,
Feng Tang <feng.tang@intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH] x86/fpu/xstate: Fix PKRU covert channel
Date: Thu, 31 Aug 2023 12:12:22 -0700 [thread overview]
Message-ID: <c71199d1-93b3-ff51-f571-34d60cd36c1c@intel.com> (raw)
In-Reply-To: <20230831043228.1194256-1-jmattson@google.com>
On 8/30/23 21:32, Jim Mattson wrote:
> When XCR0[9] is set, PKRU can be read and written from userspace with
> XSAVE and XRSTOR, even when CR4.PKE is clear.
>
> Clear XCR0[9] when protection keys are disabled.
>
> Reported-by: Tavis Ormandy <taviso@google.com>
> Signed-off-by: Jim Mattson <jmattson@google.com>
Is there any way to trigger this other than "nopku" on the command-line?
I'm not sure how scary this particular covert channel is, but it does
make sense to do this even if it's only to avoid wasting XSAVE space on
a feature that nobody can use (for things other than covert channels).
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
next prev parent reply other threads:[~2023-08-31 19:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-31 4:32 Jim Mattson
2023-08-31 19:12 ` Dave Hansen [this message]
2023-08-31 19:28 ` Jim Mattson
2023-08-31 21:36 ` [tip: x86/urgent] " tip-bot2 for Jim Mattson
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