From: Sohil Mehta <sohil.mehta@intel.com>
To: Borislav Petkov <bp@kernel.org>, X86 ML <x86@kernel.org>
Cc: Nikunj A Dadhania <nikunj@amd.com>,
LKML <linux-kernel@vger.kernel.org>,
"Borislav Petkov (AMD)" <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>, <stable@kernel.org>
Subject: Re: [PATCH 2/4] x86/cpu: Remove X86_CR4_FRED from the CR4 pinned bits mask
Date: Fri, 20 Mar 2026 10:49:41 -0700 [thread overview]
Message-ID: <b1bbc71c-3a0c-4ee8-8df7-64498223b9a6@intel.com> (raw)
In-Reply-To: <20260320115417.4156-3-bp@kernel.org>
On 3/20/2026 4:54 AM, Borislav Petkov wrote:
> So, instead, remove the FRED bit from the CR4 pinning mask, thus
> obviating the need to temporarily disable CR4 pinning.
>
> If someone manages to disable FRED when poking at CR4, then
> idt_invalidate() would make sure the system would crash'n'burn on the
> first exception triggered, which is a much better outcome security-wise.
>
> Fixes: ff45746fbf00 ("x86/cpu: Add X86_CR4_FRED macro")
> Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> Cc: <stable@kernel.org> # 6.12+
> Link: https://lore.kernel.org/r/177385987098.1647592.3381141860481415647.tip-bot2@tip-bot2
> ---
> arch/x86/kernel/cpu/common.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
next prev parent reply other threads:[~2026-03-20 17:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 11:54 [PATCH 0/4] x86/CPU: Fix CR4 pinning and FRED in CoCo guests Borislav Petkov
2026-03-20 11:54 ` [PATCH 1/4] x86/cpu: Enable FSGSBASE early in cpu_init_exception_handling() Borislav Petkov
2026-03-20 11:54 ` [PATCH 2/4] x86/cpu: Remove X86_CR4_FRED from the CR4 pinned bits mask Borislav Petkov
2026-03-20 17:49 ` Sohil Mehta [this message]
2026-03-20 11:54 ` [PATCH 3/4] x86/fred: Fix early boot failures on SEV-ES/SNP guests Borislav Petkov
2026-03-20 11:54 ` [PATCH 4/4] x86/cpu: Add comment clarifying CRn pinning Borislav Petkov
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