Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753850AbcCHINL (ORCPT ); Tue, 8 Mar 2016 03:13:11 -0500 Received: from torg.zytor.com ([198.137.202.12]:40610 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932065AbcCHIM5 (ORCPT ); Tue, 8 Mar 2016 03:12:57 -0500 Date: Tue, 8 Mar 2016 00:12:37 -0800 From: tip-bot for Chris Bainbridge Message-ID: Cc: mingo@kernel.org, bp@suse.de, tglx@linutronix.de, linux-kernel@vger.kernel.org, chris.bainbridge@gmail.com, hpa@zytor.com Reply-To: mingo@kernel.org, bp@suse.de, chris.bainbridge@gmail.com, linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de In-Reply-To: <1456834359-5132-1-git-send-email-chris.bainbridge@gmail.com> References: <1456834359-5132-1-git-send-email-chris.bainbridge@gmail.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/microcode] x86/microcode/intel: Change checksum variables to u32 Git-Commit-ID: bc864af13f34d19c911f5691d87bdacc9ce109f5 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3510 Lines: 95 Commit-ID: bc864af13f34d19c911f5691d87bdacc9ce109f5 Gitweb: http://git.kernel.org/tip/bc864af13f34d19c911f5691d87bdacc9ce109f5 Author: Chris Bainbridge AuthorDate: Mon, 7 Mar 2016 11:10:00 +0100 Committer: Thomas Gleixner CommitDate: Tue, 8 Mar 2016 09:08:44 +0100 x86/microcode/intel: Change checksum variables to u32 Microcode checksum verification should be done using unsigned 32-bit values otherwise the calculation overflow results in undefined behaviour. This is also nicely documented in the SDM, section "Microcode Update Checksum": "To check for a corrupt microcode update, software must perform a unsigned DWORD (32-bit) checksum of the microcode update. Even though some fields are signed, the checksum procedure treats all DWORDs as unsigned. Microcode updates with a header version equal to 00000001H must sum all DWORDs that comprise the microcode update. A valid checksum check will yield a value of 00000000H." but for some reason the code has been using ints from the very beginning. In practice, this bug possibly manifested itself only when doing the microcode data checksum - apparently, currently shipped Intel microcode doesn't have an extended signature table for which we do checksum verification too. UBSAN: Undefined behaviour in arch/x86/kernel/cpu/microcode/intel_lib.c:105:12 signed integer overflow: -1500151068 + -2125470173 cannot be represented in type 'int' CPU: 0 PID: 0 Comm: swapper Not tainted 4.5.0-rc5+ #495 ... Call Trace: dump_stack ? inotify_ioctl ubsan_epilogue handle_overflow __ubsan_handle_add_overflow microcode_sanity_check get_matching_model_microcode.isra.2.constprop.8 ? early_idt_handler_common ? strlcpy ? find_cpio_data load_ucode_intel_bsp load_ucode_bsp ? load_ucode_bsp x86_64_start_kernel [ Expand and massage commit message. ] Signed-off-by: Chris Bainbridge Signed-off-by: Borislav Petkov Cc: hmh@hmh.eng.br Link: http://lkml.kernel.org/r/1456834359-5132-1-git-send-email-chris.bainbridge@gmail.com Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/microcode/intel_lib.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/intel_lib.c b/arch/x86/kernel/cpu/microcode/intel_lib.c index b96896b..99ca2c9 100644 --- a/arch/x86/kernel/cpu/microcode/intel_lib.c +++ b/arch/x86/kernel/cpu/microcode/intel_lib.c @@ -49,7 +49,7 @@ int microcode_sanity_check(void *mc, int print_err) unsigned long total_size, data_size, ext_table_size; struct microcode_header_intel *mc_header = mc; struct extended_sigtable *ext_header = NULL; - int sum, orig_sum, ext_sigcount = 0, i; + u32 sum, orig_sum, ext_sigcount = 0, i; struct extended_signature *ext_sig; total_size = get_totalsize(mc_header); @@ -85,8 +85,8 @@ int microcode_sanity_check(void *mc, int print_err) /* check extended table checksum */ if (ext_table_size) { - int ext_table_sum = 0; - int *ext_tablep = (int *)ext_header; + u32 ext_table_sum = 0; + u32 *ext_tablep = (u32 *)ext_header; i = ext_table_size / DWSIZE; while (i--) @@ -102,7 +102,7 @@ int microcode_sanity_check(void *mc, int print_err) orig_sum = 0; i = (MC_HEADER_SIZE + data_size) / DWSIZE; while (i--) - orig_sum += ((int *)mc)[i]; + orig_sum += ((u32 *)mc)[i]; if (orig_sum) { if (print_err) pr_err("aborting, bad checksum\n");