Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752294AbdHSA2w (ORCPT ); Fri, 18 Aug 2017 20:28:52 -0400 Received: from mga07.intel.com ([134.134.136.100]:43538 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751706AbdHSA2i (ORCPT ); Fri, 18 Aug 2017 20:28:38 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,394,1498546800"; d="scan'208";a="1164119658" From: Ricardo Neri To: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , Borislav Petkov Cc: Peter Zijlstra , Andrew Morton , Brian Gerst , Chris Metcalf , Dave Hansen , Paolo Bonzini , Liang Z Li , Masami Hiramatsu , Huang Rui , Jiri Slaby , Jonathan Corbet , "Michael S. Tsirkin" , Paul Gortmaker , Vlastimil Babka , Chen Yucong , "Ravi V. Shankar" , Shuah Khan , linux-kernel@vger.kernel.org, x86@kernel.org, ricardo.neri@intel.com, Ricardo Neri , Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Nathan Howard , Adan Hawthorn , Joe Perches Subject: [PATCH v8 05/28] x86/mpx: Use signed variables to compute effective addresses Date: Fri, 18 Aug 2017 17:27:46 -0700 Message-Id: <20170819002809.111312-6-ricardo.neri-calderon@linux.intel.com> X-Mailer: git-send-email 2.13.0 In-Reply-To: <20170819002809.111312-1-ricardo.neri-calderon@linux.intel.com> References: <20170819002809.111312-1-ricardo.neri-calderon@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2845 Lines: 82 Even though memory addresses are unsigned, the operands used to compute the effective address do have a sign. This is true for ModRM.rm, SIB.base, SIB.index as well as the displacement bytes. Thus, signed variables shall be used when computing the effective address from these operands. Once the signed effective address has been computed, it is casted to an unsigned long to determine the linear address. Variables are renamed to better reflect the type of address being computed. Cc: Borislav Petkov Cc: Andy Lutomirski Cc: Dave Hansen Cc: Adam Buchbinder Cc: Colin Ian King Cc: Lorenzo Stoakes Cc: Qiaowei Ren Cc: Peter Zijlstra Cc: Nathan Howard Cc: Adan Hawthorn Cc: Joe Perches Cc: Ravi V. Shankar Cc: x86@kernel.org Signed-off-by: Ricardo Neri --- arch/x86/mm/mpx.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 9ceaa955d2ba..9eec98022510 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -138,8 +138,9 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, */ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) { - unsigned long addr, base, indx; int addr_offset, base_offset, indx_offset; + unsigned long linear_addr; + long eff_addr, base, indx; insn_byte_t sib; insn_get_modrm(insn); @@ -150,7 +151,8 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); if (addr_offset < 0) goto out_err; - addr = regs_get_register(regs, addr_offset); + + eff_addr = regs_get_register(regs, addr_offset); } else { if (insn->sib.nbytes) { base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); @@ -163,16 +165,22 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) base = regs_get_register(regs, base_offset); indx = regs_get_register(regs, indx_offset); - addr = base + indx * (1 << X86_SIB_SCALE(sib)); + + eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); } else { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); if (addr_offset < 0) goto out_err; - addr = regs_get_register(regs, addr_offset); + + eff_addr = regs_get_register(regs, addr_offset); } - addr += insn->displacement.value; + + eff_addr += insn->displacement.value; } - return (void __user *)addr; + + linear_addr = (unsigned long)eff_addr; + + return (void __user *)linear_addr; out_err: return (void __user *)-1; } -- 2.13.0