Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752123AbbEBTH6 (ORCPT ); Sat, 2 May 2015 15:07:58 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44238 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752023AbbEBTHz (ORCPT ); Sat, 2 May 2015 15:07:55 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Masami Hiramatsu , Dave Hansen , Ingo Molnar Subject: [PATCH 4.0 012/220] x86/asm/decoder: Fix and enforce max instruction size in the insn decoder Date: Sat, 2 May 2015 20:58:47 +0200 Message-Id: <20150502185854.905386886@linuxfoundation.org> X-Mailer: git-send-email 2.3.7 In-Reply-To: <20150502185854.333748961@linuxfoundation.org> References: <20150502185854.333748961@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2363 Lines: 68 4.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit 91e5ed49fca09c2b83b262b9757d1376ee2b46c3 upstream. x86 instructions cannot exceed 15 bytes, and the instruction decoder should enforce that. Prior to 6ba48ff46f76, the instruction length limit was implicitly set to 16, which was an approximation of 15, but there is currently no limit at all. Fix MAX_INSN_SIZE (it should be 15, not 16), and fix the decoder to reject instructions that exceed MAX_INSN_SIZE. Other than potentially confusing some of the decoder sanity checks, I'm not aware of any actual problems that omitting this check would cause, nor am I aware of any practical problems caused by the MAX_INSN_SIZE error. Signed-off-by: Andy Lutomirski Acked-by: Masami Hiramatsu Cc: Dave Hansen Fixes: 6ba48ff46f76 ("x86: Remove arbitrary instruction size limit ... Link: http://lkml.kernel.org/r/f8f0bc9b8c58cfd6830f7d88400bf1396cbdcd0f.1422403511.git.luto@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/insn.h | 2 +- arch/x86/lib/insn.c | 7 +++++++ 2 files changed, 8 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/insn.h +++ b/arch/x86/include/asm/insn.h @@ -69,7 +69,7 @@ struct insn { const insn_byte_t *next_byte; }; -#define MAX_INSN_SIZE 16 +#define MAX_INSN_SIZE 15 #define X86_MODRM_MOD(modrm) (((modrm) & 0xc0) >> 6) #define X86_MODRM_REG(modrm) (((modrm) & 0x38) >> 3) --- a/arch/x86/lib/insn.c +++ b/arch/x86/lib/insn.c @@ -52,6 +52,13 @@ */ void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64) { + /* + * Instructions longer than MAX_INSN_SIZE (15 bytes) are invalid + * even if the input buffer is long enough to hold them. + */ + if (buf_len > MAX_INSN_SIZE) + buf_len = MAX_INSN_SIZE; + memset(insn, 0, sizeof(*insn)); insn->kaddr = kaddr; insn->end_kaddr = kaddr + buf_len; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/