From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7CAE34FF4B; Tue, 16 Dec 2025 11:47:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765885675; cv=none; b=d8mjFfHikbRjOXnQudiQT/v/i/4MZh9XqDM4tNLanvqqaPeAUmZ10+rVvew/+fDBQ4m/3L4K/fUR6UKrCZV/8m8Toi3Vf76yLKUcp81fr4oohjIHsYNg/3J/HUUtnlon3YbzCu/9gYKouX6YWOWgiSP8mXfoBlFKAbuh0wWFQcU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765885675; c=relaxed/simple; bh=3T1jpHFvlSeXTRILvT7QTLcD7fTpRysRqhYIjUixr6c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ehylsM005/iDcZocaSS1H1mg9d3uv8FEeWa0/mcVWEZGC+eSVcvokL3lnYdCV4FXOy8Le+HpcKlAhIGViwie6HXgP2nwyLXhBqAaMUVlqwl1yWtAGZAZfF21t8Wkvrj1w0yOay3WA43sVwZXY4erT7by//tR6xbM2xrOjG4OPa0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SQTlEnCc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="SQTlEnCc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58091C4CEF1; Tue, 16 Dec 2025 11:47:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765885674; bh=3T1jpHFvlSeXTRILvT7QTLcD7fTpRysRqhYIjUixr6c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SQTlEnCc/SVF5WM/XEqeMH9fwXF1W0lgYEYxauQP7xH17+DxFlKffEAr0pDaX5UEM eTcn/n7HSFVWPz7Cq96kU1uOSHkqmcXNvBEK3y1PV4WqO5V1hYwCM51Q/J9ZqDqClV iVU0cqNNhZA1XfTo2vzAEmjnA/qm+I9cmDCHqnGA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Michael van der Westhuizen , Tobias Fleig , Kiryl Shutsemau , Usama Arif , "Borislav Petkov (AMD)" , Ard Biesheuvel , Dave Hansen , Sasha Levin Subject: [PATCH 6.17 177/507] x86/boot: Fix page table access in 5-level to 4-level paging transition Date: Tue, 16 Dec 2025 12:10:18 +0100 Message-ID: <20251216111351.928911587@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251216111345.522190956@linuxfoundation.org> References: <20251216111345.522190956@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Usama Arif [ Upstream commit eb2266312507d7b757859e2227aa5c4ba6280ebe ] When transitioning from 5-level to 4-level paging, the existing code incorrectly accesses page table entries by directly dereferencing CR3 and applying PAGE_MASK. This approach has several issues: - __native_read_cr3() returns the raw CR3 register value, which on x86_64 includes not just the physical address but also flags. Bits above the physical address width of the system i.e. above __PHYSICAL_MASK_SHIFT) are also not masked. - The PGD entry is masked by PAGE_SIZE which doesn't take into account the higher bits such as _PAGE_BIT_NOPTISHADOW. Replace this with proper accessor functions: - native_read_cr3_pa(): Uses CR3_ADDR_MASK to additionally mask metadata out of CR3 (like SME or LAM bits). All remaining bits are real address bits or reserved and must be 0. - mask pgd value with PTE_PFN_MASK instead of PAGE_MASK, accounting for flags above bit 51 (_PAGE_BIT_NOPTISHADOW in particular). Bits below 51, but above the max physical address are reserved and must be 0. Fixes: e9d0e6330eb8 ("x86/boot/compressed/64: Prepare new top-level page table for trampoline") Reported-by: Michael van der Westhuizen Reported-by: Tobias Fleig Co-developed-by: Kiryl Shutsemau Signed-off-by: Kiryl Shutsemau Signed-off-by: Usama Arif Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Ard Biesheuvel Acked-by: Dave Hansen Link: https://lore.kernel.org/r/a482fd68-ce54-472d-8df1-33d6ac9f6bb5@intel.com Signed-off-by: Sasha Levin --- arch/x86/boot/compressed/pgtable_64.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index bdd26050dff77..0e89e197e1126 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -3,6 +3,7 @@ #include #include #include +#include #include #include "../string.h" #include "efi.h" @@ -168,9 +169,10 @@ asmlinkage void configure_5level_paging(struct boot_params *bp, void *pgtable) * For 4- to 5-level paging transition, set up current CR3 as * the first and the only entry in a new top-level page table. */ - *trampoline_32bit = __native_read_cr3() | _PAGE_TABLE_NOENC; + *trampoline_32bit = native_read_cr3_pa() | _PAGE_TABLE_NOENC; } else { - unsigned long src; + u64 *new_cr3; + pgd_t *pgdp; /* * For 5- to 4-level paging transition, copy page table pointed @@ -180,8 +182,9 @@ asmlinkage void configure_5level_paging(struct boot_params *bp, void *pgtable) * We cannot just point to the page table from trampoline as it * may be above 4G. */ - src = *(unsigned long *)__native_read_cr3() & PAGE_MASK; - memcpy(trampoline_32bit, (void *)src, PAGE_SIZE); + pgdp = (pgd_t *)native_read_cr3_pa(); + new_cr3 = (u64 *)(native_pgd_val(pgdp[0]) & PTE_PFN_MASK); + memcpy(trampoline_32bit, new_cr3, PAGE_SIZE); } toggle_la57(trampoline_32bit); -- 2.51.0