From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754619Ab0EXOho (ORCPT ); Mon, 24 May 2010 10:37:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58923 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752878Ab0EXOhm (ORCPT ); Mon, 24 May 2010 10:37:42 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20100522165401.GB19573@redhat.com> References: <20100522165401.GB19573@redhat.com> <1266280229-18469-1-git-send-email-vapier@gentoo.org> <1274431345-22366-1-git-send-email-vapier@gentoo.org> <20100521162659.GA16193@redhat.com> <20100521183512.4477F40476@magilla.sf.frob.com> <20100522165320.GA19573@redhat.com> To: Oleg Nesterov Cc: dhowells@redhat.com, Roland McGrath , Andrew Morton , Mike Frysinger , linux-sh@vger.kernel.org, Paul Mundt , uclinux-dist-devel@blackfin.uclinux.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm 1/1] ptrace: PTRACE_GETFDPIC: fix the unsafe usage of child->mm Date: Mon, 24 May 2010 15:36:57 +0100 Message-ID: <25539.1274711817@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oleg Nesterov wrote: > Now that Mike Frysinger unified the FDPIC ptrace code, we can fix > the unsafe usage of child->mm in ptrace_request(PTRACE_GETFDPIC). > > We have the reference to task_struct, and ptrace_check_attach() > verified the tracee is stopped. But nothing can protect from > SIGKILL after that, we must not assume child->mm != NULL. > > Signed-off-by: Oleg Nesterov Acked-by: David Howells Does it make sense to move the call to get_task_mm() up to sys_ptrace() since several ptrace functions use it? The mm pointer could then be handed down the ptrace hierarchy. David