Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753454AbdH2QJ1 (ORCPT ); Tue, 29 Aug 2017 12:09:27 -0400 Received: from mx2.suse.de ([195.135.220.15]:48680 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751670AbdH2QJZ (ORCPT ); Tue, 29 Aug 2017 12:09:25 -0400 Date: Tue, 29 Aug 2017 18:09:06 +0200 From: Borislav Petkov To: Ricardo Neri Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andy Lutomirski , 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, Adam Buchbinder , Colin Ian King , Lorenzo Stoakes , Qiaowei Ren , Nathan Howard , Adan Hawthorn , Joe Perches Subject: Re: [PATCH v8 05/28] x86/mpx: Use signed variables to compute effective addresses Message-ID: <20170829160906.gpenny6yqq5squ6l@pd.tnic> References: <20170819002809.111312-1-ricardo.neri-calderon@linux.intel.com> <20170819002809.111312-6-ricardo.neri-calderon@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170819002809.111312-6-ricardo.neri-calderon@linux.intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3207 Lines: 93 On Fri, Aug 18, 2017 at 05:27:46PM -0700, Ricardo Neri wrote: > 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(-) I think you can simplify this function even more (diff ontop): diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 9eec98022510..d0ec5c9b2a57 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -139,7 +139,7 @@ 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) { int addr_offset, base_offset, indx_offset; - unsigned long linear_addr; + unsigned long linear_addr = -1; long eff_addr, base, indx; insn_byte_t sib; @@ -150,18 +150,18 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) if (X86_MODRM_MOD(insn->modrm.value) == 3) { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); if (addr_offset < 0) - goto out_err; + goto out; eff_addr = regs_get_register(regs, addr_offset); } else { if (insn->sib.nbytes) { base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); if (base_offset < 0) - goto out_err; + goto out; indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX); if (indx_offset < 0) - goto out_err; + goto out; base = regs_get_register(regs, base_offset); indx = regs_get_register(regs, indx_offset); @@ -170,7 +170,7 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) } else { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); if (addr_offset < 0) - goto out_err; + goto out; eff_addr = regs_get_register(regs, addr_offset); } @@ -180,9 +180,8 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) linear_addr = (unsigned long)eff_addr; +out: return (void __user *)linear_addr; -out_err: - return (void __user *)-1; } static int mpx_insn_decode(struct insn *insn, -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --