Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932235AbaF1SWm (ORCPT ); Sat, 28 Jun 2014 14:22:42 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54039 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755801AbaF1RvW (ORCPT ); Sat, 28 Jun 2014 13:51:22 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , Catalin Marinas Subject: [PATCH 3.15 035/139] arm64: ptrace: change fs when passing kernel pointer to regset code Date: Sat, 28 Jun 2014 10:46:36 -0700 Message-Id: <20140628174607.027338147@linuxfoundation.org> X-Mailer: git-send-email 2.0.1 In-Reply-To: <20140628174605.352098823@linuxfoundation.org> References: <20140628174605.352098823@linuxfoundation.org> User-Agent: quilt/0.63-1 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 3.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon commit c168870704bcde6bb63d05f7882b620dd3985a46 upstream. Our compat PTRACE_POKEUSR implementation simply passes the user data to regset_copy_from_user after some simple range checking. Unfortunately, the data in question has already been copied to the kernel stack by this point, so the subsequent access_ok check fails and the ptrace request returns -EFAULT. This causes problems tracing fork() with older versions of strace. This patch briefly changes the fs to KERNEL_DS, so that the access_ok check passes even with a kernel address. Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/ptrace.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -821,6 +821,7 @@ static int compat_ptrace_write_user(stru compat_ulong_t val) { int ret; + mm_segment_t old_fs = get_fs(); if (off & 3 || off >= COMPAT_USER_SZ) return -EIO; @@ -828,10 +829,13 @@ static int compat_ptrace_write_user(stru if (off >= sizeof(compat_elf_gregset_t)) return 0; + set_fs(KERNEL_DS); ret = copy_regset_from_user(tsk, &user_aarch32_view, REGSET_COMPAT_GPR, off, sizeof(compat_ulong_t), &val); + set_fs(old_fs); + return ret; } -- 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/