Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755396Ab1DVNQh (ORCPT ); Fri, 22 Apr 2011 09:16:37 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:59262 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752407Ab1DVNQg (ORCPT ); Fri, 22 Apr 2011 09:16:36 -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=ngoj7QuQ2ZSc8q5Hw45tkrYhIyCcvmIa/xGdT+FB7OpF5ra4z4VR3KChuMmdyv2Yam Rcw+NXQNshAwB6o8mWEzQrlTXmneMEbEgXptp1eYSCnkZD+/gaWcoIcqGzE9/lExKxqt nMB3dS6lGgY504F6QEaobofJmXvZ7R62r/Q1w= From: Frederic Weisbecker To: LPPC Cc: LKML , Frederic Weisbecker , Oleg Nesterov , Ingo Molnar , Benjamin Herrenschmidt , Peter Zijlstra , Will Deacon , Prasad , Paul Mundt , "v2.6.33.." Subject: [PATCH 3/5] powerpc, hw_breakpoints: Fix racy access to ptrace breakpoints Date: Fri, 22 Apr 2011 15:16:27 +0200 Message-Id: <1303478187-2367-1-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.3.2 In-Reply-To: <1302284067-7860-4-git-send-email-fweisbec@gmail.com> References: <1302284067-7860-4-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: 1507 Lines: 45 (resend with ppc list in cc) 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: Benjamin Herrenschmidt Cc: Peter Zijlstra Cc: Will Deacon Cc: Prasad Cc: Paul Mundt Cc: v2.6.33.. --- arch/powerpc/kernel/ptrace.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c index 55613e3..4edeeb3 100644 --- a/arch/powerpc/kernel/ptrace.c +++ b/arch/powerpc/kernel/ptrace.c @@ -1591,7 +1591,10 @@ long arch_ptrace(struct task_struct *child, long request, } case PTRACE_SET_DEBUGREG: + if (ptrace_get_breakpoints(child) < 0) + return -ESRCH; ret = ptrace_set_debugreg(child, addr, data); + ptrace_put_breakpoints(child); break; #ifdef CONFIG_PPC64 -- 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/