Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965443AbeAOMiy (ORCPT + 1 other); Mon, 15 Jan 2018 07:38:54 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:45676 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965155AbeAOMiu (ORCPT ); Mon, 15 Jan 2018 07:38:50 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Maciej W. Rozycki" , James Hogan , Paul Burton , Alex Smith , Dave Martin , linux-mips@linux-mips.org, Ralf Baechle Subject: [PATCH 4.4 07/87] MIPS: Guard against any partial write attempt with PTRACE_SETREGSET Date: Mon, 15 Jan 2018 13:34:06 +0100 Message-Id: <20180115123350.055682453@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180115123349.252309699@linuxfoundation.org> References: <20180115123349.252309699@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Maciej W. Rozycki commit dc24d0edf33c3e15099688b6bbdf7bdc24bf6e91 upstream. Complement commit d614fd58a283 ("mips/ptrace: Preserve previous registers for short regset write") and ensure that no partial register write attempt is made with PTRACE_SETREGSET, as we do not preinitialize any temporaries used to hold incoming register data and consequently random data could be written. It is the responsibility of the caller, such as `ptrace_regset', to arrange for writes to span whole registers only, so here we only assert that it has indeed happened. Signed-off-by: Maciej W. Rozycki Fixes: 72b22bbad1e7 ("MIPS: Don't assume 64-bit FP registers for FP regset") Cc: James Hogan Cc: Paul Burton Cc: Alex Smith Cc: Dave Martin Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17926/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/ptrace.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -536,7 +536,15 @@ static int fpr_set_msa(struct task_struc return 0; } -/* Copy the supplied NT_PRFPREG buffer to the floating-point context. */ +/* + * Copy the supplied NT_PRFPREG buffer to the floating-point context. + * + * We optimize for the case where `count % sizeof(elf_fpreg_t) == 0', + * which is supposed to have been guaranteed by the kernel before + * calling us, e.g. in `ptrace_regset'. We enforce that requirement, + * so that we can safely avoid preinitializing temporaries for + * partial register writes. + */ static int fpr_set(struct task_struct *target, const struct user_regset *regset, unsigned int pos, unsigned int count, @@ -544,6 +552,8 @@ static int fpr_set(struct task_struct *t { int err; + BUG_ON(count % sizeof(elf_fpreg_t)); + /* XXX fcr31 */ init_fp_ctx(target);