Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758482AbZFWWkp (ORCPT ); Tue, 23 Jun 2009 18:40:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757501AbZFWWkg (ORCPT ); Tue, 23 Jun 2009 18:40:36 -0400 Received: from mx2.redhat.com ([66.187.237.31]:54562 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756424AbZFWWkf (ORCPT ); Tue, 23 Jun 2009 18:40:35 -0400 Date: Tue, 23 Jun 2009 21:25:32 +0200 From: Oleg Nesterov To: Andrew Morton , Christoph Hellwig Cc: James Morris , Ingo Molnar , Chris Wright , Roland McGrath , linux-kernel@vger.kernel.org, Al Viro , linux-security-module@vger.kernel.org Subject: [PATCH 1/1] mm_for_maps: simplify, use ptrace_may_access() Message-ID: <20090623192532.GB27853@redhat.com> References: <20090507083851.GA19133@elte.hu> <20090507085742.GB3036@sequoia.sous-sol.org> <20090507090459.GE19133@elte.hu> <20090507092009.GC3036@sequoia.sous-sol.org> <20090507102015.GB8901@elte.hu> <20090623141451.GA8133@redhat.com> <20090623174918.GA24430@infradead.org> <20090623192451.GA27853@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090623192451.GA27853@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1714 Lines: 55 It would be nice to kill __ptrace_may_access(). It requires task_lock(), but this lock is only needed to read mm->flags in the middle. Convert mm_for_maps() to use ptrace_may_access(), this also simplifies the code a little bit. Also, we do not need to take ->mmap_sem in advance. In fact I think mm_for_maps() should not play with ->mmap_sem at all, the caller should take this lock. With or without this patch, without ->cred_guard_mutex held we can race with exec() and get the new ->mm but check old creds. Signed-off-by: Oleg Nesterov --- WAIT/fs/proc/base.c~1_MM_FOR_MAPS 2009-06-17 14:11:26.000000000 +0200 +++ WAIT/fs/proc/base.c 2009-06-23 20:16:44.000000000 +0200 @@ -237,20 +237,19 @@ struct mm_struct *mm_for_maps(struct tas struct mm_struct *mm = get_task_mm(task); if (!mm) return NULL; + if (mm != current->mm) { + /* + * task->mm can be changed before security check, + * in that case we must notice the change after. + */ + if (!ptrace_may_access(task, PTRACE_MODE_READ) || + mm != task->mm) { + mmput(mm); + return NULL; + } + } down_read(&mm->mmap_sem); - task_lock(task); - if (task->mm != mm) - goto out; - if (task->mm != current->mm && - __ptrace_may_access(task, PTRACE_MODE_READ) < 0) - goto out; - task_unlock(task); return mm; -out: - task_unlock(task); - up_read(&mm->mmap_sem); - mmput(mm); - return NULL; } static int proc_pid_cmdline(struct task_struct *task, char * buffer) -- 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/