Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757296Ab1DHRfW (ORCPT ); Fri, 8 Apr 2011 13:35:22 -0400 Received: from mail-qy0-f181.google.com ([209.85.216.181]:60223 "EHLO mail-qy0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757188Ab1DHRfT (ORCPT ); Fri, 8 Apr 2011 13:35:19 -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=tD1ARQ7ktImiKptV950BO6+hLIBe3/sgCz2fEH6WIOg1cG2N1AsTjrvhpJfV+V2aOn d+o+fCzB5+G8bv4xAHfsGzTjqS+p4WAryVhs8POJrJnf+RhLAfeuxKLiZRGRuQaL3QOR r+cFW9isqc3t6n721AePpkx58NALnMIJckEbM= From: Frederic Weisbecker To: LKML Cc: LKML , Frederic Weisbecker , Ingo Molnar , Peter Zijlstra , Will Deacon , Prasad , Paul Mundt Subject: [PATCH 4/5] arm, hw_breakpoints: Fix racy access to ptrace breakpoints Date: Fri, 8 Apr 2011 19:34:26 +0200 Message-Id: <1302284067-7860-5-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.3.2 In-Reply-To: <1302284067-7860-1-git-send-email-fweisbec@gmail.com> References: <1302284067-7860-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1642 Lines: 51 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 Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Will Deacon Cc: Prasad Cc: Paul Mundt --- 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 -- 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/