From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail333.us4.mandrillapp.com ([205.201.137.77]:58676 "EHLO mail333.us4.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756020AbcCAX4n (ORCPT ); Tue, 1 Mar 2016 18:56:43 -0500 Received: from pmta03.dal05.mailchimp.com (127.0.0.1) by mail333.us4.mandrillapp.com id hqom3m174not for ; Tue, 1 Mar 2016 23:54:37 +0000 (envelope-from ) From: Greg Kroah-Hartman Subject: [PATCH 4.4 158/342] MIPS: Fix buffer overflow in syscall_get_arguments() To: Cc: Greg Kroah-Hartman , , Milko Leporis , James Hogan , , Ralf Baechle Message-Id: <20160301234533.074219876@linuxfoundation.org> In-Reply-To: <20160301234527.990448862@linuxfoundation.org> References: <20160301234527.990448862@linuxfoundation.org> Date: Tue, 01 Mar 2016 23:54:36 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: James Hogan commit f4dce1ffd2e30fa31756876ef502ce6d2324be35 upstream. Since commit 4c21b8fd8f14 ("MIPS: seccomp: Handle indirect system calls (o32)"), syscall_get_arguments() attempts to handle o32 indirect syscall arguments by incrementing both the start argument number and the number of arguments to fetch. However only the start argument number needs to be incremented. The number of arguments does not change, they're just shifted up by one, and in fact the output array is provided by the caller and is likely only n entries long, so reading more arguments overflows the output buffer. In the case of seccomp, this results in it fetching 7 arguments starting at the 2nd one, which overflows the unsigned long args[6] in populate_seccomp_data(). This clobbers the $s0 register from syscall_trace_enter() which __seccomp_phase1_filter() saved onto the stack, into which syscall_trace_enter() had placed its syscall number argument. This caused Chromium to crash. Credit goes to Milko for tracking it down as far as $s0 being clobbered. Fixes: 4c21b8fd8f14 ("MIPS: seccomp: Handle indirect system calls (o32)") Reported-by: Milko Leporis Signed-off-by: James Hogan Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/12213/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/include/asm/syscall.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/arch/mips/include/asm/syscall.h +++ b/arch/mips/include/asm/syscall.h @@ -101,10 +101,8 @@ static inline void syscall_get_arguments /* O32 ABI syscall() - Either 64-bit with O32 or 32-bit */ if ((config_enabled(CONFIG_32BIT) || test_tsk_thread_flag(task, TIF_32BIT_REGS)) && - (regs->regs[2] == __NR_syscall)) { + (regs->regs[2] == __NR_syscall)) i++; - n++; - } while (n--) ret |= mips_get_syscall_arg(args++, task, regs, i++);