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 92AB630FF1D; Fri, 9 Jan 2026 11:53:58 +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=1767959638; cv=none; b=Mu9VCH36P1sK73E74ITQn6Lqe6utljpVD3zNA2acZPWiC9elGCFXxLHUMebOYXlvhOGoSV8tOxgACHR0oNDMol4hRnlVwWLNo9g8DGnu2lOPnkHgKYhm0s3qkaEibKQ+5af6rM0OgHioVmqv6rSX5RIwprfHJA9yW1//mrh6dxk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767959638; c=relaxed/simple; bh=OuYhcT9C74BNhLAy8WDI+XOGMMi+69S2dGm55CgizDc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eHUBqyizy2o1ahD4ifYa0nClBojZzzW8PyGpk3e55mKNTV85cKYOqZDYkCnCzsRxGWUwSCM8xUDzkXmGJrsNaT2coRnGsD82dptW0vdGcOfcz8ziJ7vMKz5vabzVdZPb3JiW72ygb8kLL7NkaKE8NoUonC7c1aEl7Hg7Wvyk0q8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SBPucIse; 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="SBPucIse" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 210D4C4CEF1; Fri, 9 Jan 2026 11:53:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767959638; bh=OuYhcT9C74BNhLAy8WDI+XOGMMi+69S2dGm55CgizDc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SBPucIse6DqGF0EaHgE7wArob/5mn259ZAPFhCPBXyXr+LZnDDk3O403hU2H6JKFP 8KPxH9L5jO+4bYEScWTj943P750AMnSQVQsd6xbzY0GAObravODdeZBnBmD8qR61l5 FxCI4mHAaRuXwBgdE9uokQ/b/LPoKZMxJ28aSnMU= 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 6.6 123/737] x86/boot: Fix page table access in 5-level to 4-level paging transition Date: Fri, 9 Jan 2026 12:34:22 +0100 Message-ID: <20260109112138.630558875@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112133.973195406@linuxfoundation.org> References: <20260109112133.973195406@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-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 15354673d3aa7..dc21b0d89d667 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -2,6 +2,7 @@ #include "misc.h" #include #include +#include #include #include "pgtable.h" #include "../string.h" @@ -175,9 +176,10 @@ 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 @@ -187,8 +189,9 @@ 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