From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752585Ab1ECNZ5 (ORCPT ); Tue, 3 May 2011 09:25:57 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:61196 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752370Ab1ECNZk (ORCPT ); Tue, 3 May 2011 09:25:40 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=CxF4xXjsb1C8znihkKhuAxy2AhWTwBaBYaVSzynj2R8/ZyO0qxGe17O1hgwY1S3ypw VkH9ueVQwKaQM7A9P272B4K/zGp8JR+SvmWLn9EmCPRIHeY8SH0J/mSBdhPDrQ6+O46t g4qxgzrrUjaIcRzecY+xTgsoyoJy64R+jbLBU= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Oleg Nesterov , Will Deacon , Ingo Molnar , Peter Zijlstra , Prasad , Paul Mundt Subject: [PATCH 4/5] arm, hw_breakpoints: Fix racy access to ptrace breakpoints Date: Tue, 3 May 2011 15:25:23 +0200 Message-Id: <1304429124-2376-5-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.3.2 In-Reply-To: <1304429124-2376-1-git-send-email-fweisbec@gmail.com> References: <1304429124-2376-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While the tracer accesses ptrace breakpoints, the child task may concurrently exit due to a SIGKILL and thus release its breakpoints at the same time. We can then dereference some freed pointers. To fix this, hold a reference on the child breakpoints before manipulating them. Reported-by: Oleg Nesterov Signed-off-by: Frederic Weisbecker Acked-by: Will Deacon Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Prasad Cc: Paul Mundt Link: http://lkml.kernel.org/r/1302284067-7860-5-git-send-email-fweisbec@gmail.com --- arch/arm/kernel/ptrace.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c index 2bf27f3..8182f45 100644 --- a/arch/arm/kernel/ptrace.c +++ b/arch/arm/kernel/ptrace.c @@ -767,12 +767,20 @@ long arch_ptrace(struct task_struct *child, long request, #ifdef CONFIG_HAVE_HW_BREAKPOINT case PTRACE_GETHBPREGS: + if (ptrace_get_breakpoints(child) < 0) + return -ESRCH; + ret = ptrace_gethbpregs(child, addr, (unsigned long __user *)data); + ptrace_put_breakpoints(child); break; case PTRACE_SETHBPREGS: + if (ptrace_get_breakpoints(child) < 0) + return -ESRCH; + ret = ptrace_sethbpregs(child, addr, (unsigned long __user *)data); + ptrace_put_breakpoints(child); break; #endif -- 1.7.3.2