From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vx0-f179.google.com (mail-vx0-f179.google.com [209.85.220.179]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 97B18B6F41 for ; Fri, 22 Apr 2011 23:16:39 +1000 (EST) Received: by vxi40 with SMTP id 40so525524vxi.38 for ; Fri, 22 Apr 2011 06:16:35 -0700 (PDT) From: Frederic Weisbecker To: LPPC 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> In-Reply-To: <1302284067-7860-4-git-send-email-fweisbec@gmail.com> References: <1302284067-7860-4-git-send-email-fweisbec@gmail.com> Cc: Peter Zijlstra , Frederic Weisbecker , Will Deacon , LKML , Oleg Nesterov , Paul Mundt , Ingo Molnar , Prasad , "v2.6.33.." List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , (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