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From: Jim Mattson <jmattson@google.com>
To: linux-kernel@vger.kernel.org, x86@kernel.org
Cc: Jim Mattson <jmattson@google.com>,
	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: [PATCH] x86/fpu/xstate: Fix PKRU covert channel
Date: Wed, 30 Aug 2023 21:32:21 -0700	[thread overview]
Message-ID: <20230831043228.1194256-1-jmattson@google.com> (raw)

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>
---
 arch/x86/kernel/fpu/xstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 1afbc4866b10..a27b4f7b9365 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -71,7 +71,7 @@ static unsigned short xsave_cpuid_features[] __initdata = {
 	[XFEATURE_ZMM_Hi256]			= X86_FEATURE_AVX512F,
 	[XFEATURE_Hi16_ZMM]			= X86_FEATURE_AVX512F,
 	[XFEATURE_PT_UNIMPLEMENTED_SO_FAR]	= X86_FEATURE_INTEL_PT,
-	[XFEATURE_PKRU]				= X86_FEATURE_PKU,
+	[XFEATURE_PKRU]				= X86_FEATURE_OSPKE,
 	[XFEATURE_PASID]			= X86_FEATURE_ENQCMD,
 	[XFEATURE_XTILE_CFG]			= X86_FEATURE_AMX_TILE,
 	[XFEATURE_XTILE_DATA]			= X86_FEATURE_AMX_TILE,
-- 
2.42.0.283.g2d96d420d3-goog


             reply	other threads:[~2023-08-31  4:33 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-31  4:32 Jim Mattson [this message]
2023-08-31 19:12 ` [PATCH] x86/fpu/xstate: Fix PKRU covert channel Dave Hansen
2023-08-31 19:28   ` Jim Mattson
2023-08-31 21:36 ` [tip: x86/urgent] " tip-bot2 for Jim Mattson

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