linux-kernel - [tip: x86/urgent] x86/fpu/xstate: Fix PKRU covert channel

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Message-ID: <169351776397.27769.630866137224277838.tip-bot2@tip-bot2>
Date:   Thu, 31 Aug 2023 21:36:03 -0000
From:   "tip-bot2 for Jim Mattson" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Tavis Ormandy <taviso@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/fpu/xstate: Fix PKRU covert channel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     18032b47adf1db7b7f5fb2d1344e65aafe6417df
Gitweb:        https://git.kernel.org/tip/18032b47adf1db7b7f5fb2d1344e65aafe6417df
Author:        Jim Mattson <jmattson@...gle.com>
AuthorDate:    Wed, 30 Aug 2023 21:32:21 -07:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 31 Aug 2023 23:29:49 +02:00

x86/fpu/xstate: Fix PKRU covert channel

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@...gle.com>
Signed-off-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Link: https://lore.kernel.org/r/20230831043228.1194256-1-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 1afbc48..a27b4f7 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,