From patchwork Tue Jul 20 11:14:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Herrenschmidt X-Patchwork-Id: 481833 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C32E9C07E95 for ; Tue, 20 Jul 2021 11:16:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A337C60FDB for ; Tue, 20 Jul 2021 11:16:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237290AbhGTKfi (ORCPT ); Tue, 20 Jul 2021 06:35:38 -0400 Received: from gate.crashing.org ([63.228.1.57]:33405 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237203AbhGTKfg (ORCPT ); Tue, 20 Jul 2021 06:35:36 -0400 Received: from ip6-localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 16KBE5N6017585; Tue, 20 Jul 2021 06:14:06 -0500 Message-ID: Subject: [PATCH 1/2] arm64: efi: kaslr: Fix occasional random alloc (and boot) failure From: Benjamin Herrenschmidt To: linux-arm-kernel@lists.infradead.org Cc: Ard Biesheuvel , linux-efi@vger.kernel.org, "linux-kernel@vger.kernel.org Will Deacon" Date: Tue, 20 Jul 2021 21:14:05 +1000 User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org The EFI stub random allocator used for kaslr on arm64 has a subtle bug. In function get_entry_num_slots() which counts the number of possible allocation "slots" for the image in a given chunk of free EFI memory, "last_slot" can become negative if the chunk is smaller than the requested allocation size. The test "if (first_slot > last_slot)" doesn't catch it because both first_slot and last_slot are unsigned. I chose not to make them signed to avoid problems if this is ever used on architectures where there are meaningful addresses with the top bit set. Instead, fix it with an additional test against the allocation size. This can cause a boot failure in addition to a loss of randomisation due to another bug in the arm64 stub fixed separately. Signed-off-by: Benjamin Herrenschmidt Fixes: 2ddbfc81eac8 (efi: stub: add implementation of efi_random_alloc()) Acked-by: Ard Biesheuvel --- drivers/firmware/efi/libstub/randomalloc.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c index a408df474d83..724155b9e10d 100644 --- a/drivers/firmware/efi/libstub/randomalloc.c +++ b/drivers/firmware/efi/libstub/randomalloc.c @@ -30,6 +30,8 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md, region_end = min(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - 1, (u64)ULONG_MAX); + if (region_end < size) + return 0; first_slot = round_up(md->phys_addr, align); last_slot = round_down(region_end - size + 1, align); From patchwork Tue Jul 20 11:14:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Benjamin Herrenschmidt X-Patchwork-Id: 483579 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8DE2C07E9B for ; Tue, 20 Jul 2021 11:16:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D54D761165 for ; Tue, 20 Jul 2021 11:16:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236430AbhGTKfk (ORCPT ); Tue, 20 Jul 2021 06:35:40 -0400 Received: from gate.crashing.org ([63.228.1.57]:33406 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237358AbhGTKfj (ORCPT ); Tue, 20 Jul 2021 06:35:39 -0400 Received: from ip6-localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 16KBECBR017610; Tue, 20 Jul 2021 06:14:13 -0500 Message-ID: <161920fc31ec4168290ca31b3e4ac7a75ac1df6b.camel@kernel.crashing.org> Subject: [PATCH 2/2] arm64: efi: kaslr: Fix boot failure if efi_random_alloc() fails From: Benjamin Herrenschmidt To: linux-arm-kernel@lists.infradead.org Cc: Ard Biesheuvel , linux-efi@vger.kernel.org, "linux-kernel@vger.kernel.org Will Deacon" Date: Tue, 20 Jul 2021 21:14:12 +1000 User-Agent: Evolution 3.36.5-0ubuntu1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org If efi_random_alloc() fails, we still try to use EFI_KIMG_ALIGN instead of MIN_KIMG_ALIGN to check the kernel image alignment, which is incorrect, we need to fallback to MIN_KIMG_ALIGN (2M). This removes the not-that-useful min_kimg_align helper and instead uses the appropriate aligment in the respective call sites: efi_random_alloc() always wants EFI_KIMG_ALIGN as this is only used when kaslr is on, and all other cases go into alignment check code which always need to check (and enforce) MIN_KIMG_ALIGN Signed-off-by: Benjamin Herrenschmidt Fixes: 7c116db24d94 (efi/libstub/arm64: Retain 2MB kernel Image alignment if !KASLR) --- drivers/firmware/efi/libstub/arm64-stub.c | 27 ++++++++++------------- 1 file changed, 12 insertions(+), 15 deletions(-) diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c index 7bf0a7acae5e..e264ff90ba03 100644 --- a/drivers/firmware/efi/libstub/arm64-stub.c +++ b/drivers/firmware/efi/libstub/arm64-stub.c @@ -34,18 +34,6 @@ efi_status_t check_platform_features(void) return EFI_SUCCESS; } -/* - * Although relocatable kernels can fix up the misalignment with respect to - * MIN_KIMG_ALIGN, the resulting virtual text addresses are subtly out of - * sync with those recorded in the vmlinux when kaslr is disabled but the - * image required relocation anyway. Therefore retain 2M alignment unless - * KASLR is in use. - */ -static u64 min_kimg_align(void) -{ - return efi_nokaslr ? MIN_KIMG_ALIGN : EFI_KIMG_ALIGN; -} - efi_status_t handle_kernel_image(unsigned long *image_addr, unsigned long *image_size, unsigned long *reserve_addr, @@ -84,15 +72,24 @@ efi_status_t handle_kernel_image(unsigned long *image_addr, /* * If KASLR is enabled, and we have some randomness available, * locate the kernel at a randomized offset in physical memory. + * + * In that case, we don't need to preserve the 2M alignment */ - status = efi_random_alloc(*reserve_size, min_kimg_align(), + status = efi_random_alloc(*reserve_size, EFI_KIMG_ALIGN, reserve_addr, phys_seed); } else { status = EFI_OUT_OF_RESOURCES; } if (status != EFI_SUCCESS) { - if (IS_ALIGNED((u64)_text, min_kimg_align())) { + /* + * Although relocatable kernels can fix up the misalignment with respect to + * MIN_KIMG_ALIGN, the resulting virtual text addresses are subtly out of + * sync with those recorded in the vmlinux when kaslr is disabled but the + * image required relocation anyway. Therefore retain 2M alignment unless + * KASLR is in use. + */ + if (IS_ALIGNED((u64)_text, MIN_KIMG_ALIGN)) { /* * Just execute from wherever we were loaded by the * UEFI PE/COFF loader if the alignment is suitable. @@ -103,7 +100,7 @@ efi_status_t handle_kernel_image(unsigned long *image_addr, } status = efi_allocate_pages_aligned(*reserve_size, reserve_addr, - ULONG_MAX, min_kimg_align()); + ULONG_MAX, MIN_KIMG_ALIGN); if (status != EFI_SUCCESS) { efi_err("Failed to relocate kernel\n");