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 3B54B34FF4E; Tue, 16 Dec 2025 11:47:58 +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=1765885678; cv=none; b=qpSIrylokjZkLvaISIVV7hMWsp2YJvGp+8f0AlJStF1ZnsVKp1J+B192tIQj+Kt2wscxyJA1muYqMjO8cbnNUZropOomrS9egO/CWFof6zHCzutyD78vy55bIQ5RUaYZ152i9RUFgrcF7bz5suzvjrUWVCJJCMT3EEVBD48q37Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765885678; c=relaxed/simple; bh=vh8wfOeBhOPJTpctlyuavo+kSgRjl3vZzD30n2sajXI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G42apVFLqxPuqlQWbMv1LRvfHsGQNkXAAb6ltz9ajwXKet/UCXejvxFBiYkjz3FYgF3tqmgFX6kuJ/sSrk8KXitjxCADPRrbiUbTNr9ujIDTVlXEHAI+j4veGH2pgWuKPxnn3jKDAco/HxsfyekviZrD5ULU/LwxL+0K+JUUa0Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pNBZyDYt; 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="pNBZyDYt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E03AC4CEF1; Tue, 16 Dec 2025 11:47:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765885678; bh=vh8wfOeBhOPJTpctlyuavo+kSgRjl3vZzD30n2sajXI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pNBZyDYtQifwAeGr4i6MimdBjwcHnaWxaAYtjlzFp9XuZ/9Z3ZjqhcroYzoHlpy2/ viL57KeNu7dh5sJXye/gP8LqEqiXIUN6Lrmc7pKKJOFzaEDHyCMf3HXz9PyqhL3F2Q TI8E78kDpskyK714970AviVw5rqbN7uiLgcPvTfE= 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 , Sasha Levin Subject: [PATCH 6.17 178/507] efi/libstub: Fix page table access in 5-level to 4-level paging transition Date: Tue, 16 Dec 2025 12:10:19 +0100 Message-ID: <20251216111351.964780033@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 84361123413efc84b06f3441c6c827b95d902732 ] 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 value 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: cb1c9e02b0c1 ("x86/efistub: Perform 4/5 level paging switch from the stub") 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 Link: https://patch.msgid.link/20251103141002.2280812-3-usamaarif642@gmail.com Signed-off-by: Sasha Levin --- drivers/firmware/efi/libstub/x86-5lvl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/firmware/efi/libstub/x86-5lvl.c b/drivers/firmware/efi/libstub/x86-5lvl.c index f1c5fb45d5f7c..c00d0ae7ed5d5 100644 --- a/drivers/firmware/efi/libstub/x86-5lvl.c +++ b/drivers/firmware/efi/libstub/x86-5lvl.c @@ -66,7 +66,7 @@ void efi_5level_switch(void) bool have_la57 = native_read_cr4() & X86_CR4_LA57; bool need_toggle = want_la57 ^ have_la57; u64 *pgt = (void *)la57_toggle + PAGE_SIZE; - u64 *cr3 = (u64 *)__native_read_cr3(); + pgd_t *cr3 = (pgd_t *)native_read_cr3_pa(); u64 *new_cr3; if (!la57_toggle || !need_toggle) @@ -82,7 +82,7 @@ void efi_5level_switch(void) new_cr3[0] = (u64)cr3 | _PAGE_TABLE_NOENC; } else { /* take the new root table pointer from the current entry #0 */ - new_cr3 = (u64 *)(cr3[0] & PAGE_MASK); + new_cr3 = (u64 *)(native_pgd_val(cr3[0]) & PTE_PFN_MASK); /* copy the new root table if it is not 32-bit addressable */ if ((u64)new_cr3 > U32_MAX) -- 2.51.0