Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753379AbZKSS2e (ORCPT ); Thu, 19 Nov 2009 13:28:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752279AbZKSS2d (ORCPT ); Thu, 19 Nov 2009 13:28:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57880 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751634AbZKSS2c (ORCPT ); Thu, 19 Nov 2009 13:28:32 -0500 Date: Thu, 19 Nov 2009 13:28:33 -0500 From: Jeff Layton To: ebiederm@xmission.com (Eric W. Biederman) Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, pavel@ucw.cz Subject: Re: [PATCH] procfs: make /proc style symlinks behave like "normal" symlinks Message-ID: <20091119132833.30bc93a4@barsoom.rdu.redhat.com> In-Reply-To: References: <1258638251-20034-1-git-send-email-jlayton@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2102 Lines: 81 On Thu, 19 Nov 2009 09:07:16 -0800 ebiederm@xmission.com (Eric W. Biederman) wrote: > > Nacked-by: "Eric W. Biederman" > > This is broken. If the referenced file is in a different mount namespace > the path returned could point to a completely different path in your > own mount namespace. Even in your own mount namespace this makes the > proc symlinks racy and not guaranteed to return the file of interest. > > I don't see any hope of this approach ever working. > > Eric > Then is proc_pid_readlink broken in the same way? > > Jeff Layton writes: > > > -static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen) > > -{ > > - int error = -EACCES; > > - struct inode *inode = dentry->d_inode; > > + struct page *page = NULL; > > struct path path; > > + int error; > > > > /* Are we allowed to snoop on the tasks file descriptors? */ > > - if (!proc_fd_access_allowed(inode)) > > + if (!proc_fd_access_allowed(inode)) { > > + pathname = ERR_PTR(-EACCES); > > goto out; > > + } > > > > error = PROC_I(inode)->op.proc_get_link(inode, &path); > > - if (error) > > + if (error) { > > + pathname = ERR_PTR(error); > > goto out; > > + } > > + > > + page = alloc_page(GFP_HIGHUSER); > > + if (!page) { > > + pathname = ERR_PTR(-ENOMEM); > > + goto out_path_put; > > + } > > + > > + pathname = kmap(page); > > + pathname = d_path(&path, pathname, PAGE_SIZE); > > This is just nonsense. > How so? Care to elaborate? > > > + if (IS_ERR(pathname)) { > > + kunmap(page); > > + __free_page(page); > > + page = NULL; > > + } > > > > - error = do_proc_readlink(&path, buffer, buflen); > > +out_path_put: > > path_put(&path); > > out: > > - return error; > > + nd_set_link(nd, pathname); > > + return page; > > +} -- Jeff Layton -- 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/