From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [RFC v10][PATCH 09/13] Restore open file descriprtors Date: Fri, 28 Nov 2008 11:27:45 +0000 Message-ID: <20081128112745.GR28946@ZenIV.linux.org.uk> References: <1227747884-14150-1-git-send-email-orenl@cs.columbia.edu> <1227747884-14150-10-git-send-email-orenl@cs.columbia.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1227747884-14150-10-git-send-email-orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Oren Laadan Cc: Andrew Morton , Linus Torvalds , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Thomas Gleixner , Serge Hallyn , Dave Hansen , Ingo Molnar , "H. Peter Anvin" List-Id: linux-api@vger.kernel.org On Wed, Nov 26, 2008 at 08:04:40PM -0500, Oren Laadan wrote: > +/** > + * cr_attach_get_file - attach (and get) lonely file ptr to a file descriptor > + * @file: lonely file pointer > + */ > +static int cr_attach_get_file(struct file *file) > +{ > + int fd = get_unused_fd_flags(0); > + > + if (fd >= 0) { > + fsnotify_open(file->f_path.dentry); > + fd_install(fd, file); > + get_file(file); > + } > + return fd; > +} What happens if another thread closes the descriptor in question between fd_install() and get_file()? > + fd = cr_attach_file(file); /* no need to cleanup 'file' below */ > + if (fd < 0) { > + filp_close(file, NULL); > + ret = fd; > + goto out; > + } > + > + /* register new tuple in hash table */ > + ret = cr_obj_add_ref(ctx, file, parent, CR_OBJ_FILE, 0); > + if (ret < 0) > + goto out; Who said that file still exists at that point? BTW, there are shitloads of races here - references to fd and struct file * are mixed in a way that breaks *badly* if descriptor table is played with by another thread. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754415AbYK1L2J (ORCPT ); Fri, 28 Nov 2008 06:28:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752458AbYK1L14 (ORCPT ); Fri, 28 Nov 2008 06:27:56 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:42557 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752386AbYK1L1z (ORCPT ); Fri, 28 Nov 2008 06:27:55 -0500 Date: Fri, 28 Nov 2008 11:27:45 +0000 From: Al Viro To: Oren Laadan Cc: Andrew Morton , Linus Torvalds , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Thomas Gleixner , Serge Hallyn , Dave Hansen , Ingo Molnar , "H. Peter Anvin" Subject: Re: [RFC v10][PATCH 09/13] Restore open file descriprtors Message-ID: <20081128112745.GR28946@ZenIV.linux.org.uk> References: <1227747884-14150-1-git-send-email-orenl@cs.columbia.edu> <1227747884-14150-10-git-send-email-orenl@cs.columbia.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1227747884-14150-10-git-send-email-orenl@cs.columbia.edu> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 26, 2008 at 08:04:40PM -0500, Oren Laadan wrote: > +/** > + * cr_attach_get_file - attach (and get) lonely file ptr to a file descriptor > + * @file: lonely file pointer > + */ > +static int cr_attach_get_file(struct file *file) > +{ > + int fd = get_unused_fd_flags(0); > + > + if (fd >= 0) { > + fsnotify_open(file->f_path.dentry); > + fd_install(fd, file); > + get_file(file); > + } > + return fd; > +} What happens if another thread closes the descriptor in question between fd_install() and get_file()? > + fd = cr_attach_file(file); /* no need to cleanup 'file' below */ > + if (fd < 0) { > + filp_close(file, NULL); > + ret = fd; > + goto out; > + } > + > + /* register new tuple in hash table */ > + ret = cr_obj_add_ref(ctx, file, parent, CR_OBJ_FILE, 0); > + if (ret < 0) > + goto out; Who said that file still exists at that point? BTW, there are shitloads of races here - references to fd and struct file * are mixed in a way that breaks *badly* if descriptor table is played with by another thread. From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 28 Nov 2008 11:27:45 +0000 From: Al Viro Subject: Re: [RFC v10][PATCH 09/13] Restore open file descriprtors Message-ID: <20081128112745.GR28946@ZenIV.linux.org.uk> References: <1227747884-14150-1-git-send-email-orenl@cs.columbia.edu> <1227747884-14150-10-git-send-email-orenl@cs.columbia.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1227747884-14150-10-git-send-email-orenl@cs.columbia.edu> Sender: owner-linux-mm@kvack.org Return-Path: To: Oren Laadan Cc: Andrew Morton , Linus Torvalds , containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Thomas Gleixner , Serge Hallyn , Dave Hansen , Ingo Molnar , "H. Peter Anvin" List-ID: On Wed, Nov 26, 2008 at 08:04:40PM -0500, Oren Laadan wrote: > +/** > + * cr_attach_get_file - attach (and get) lonely file ptr to a file descriptor > + * @file: lonely file pointer > + */ > +static int cr_attach_get_file(struct file *file) > +{ > + int fd = get_unused_fd_flags(0); > + > + if (fd >= 0) { > + fsnotify_open(file->f_path.dentry); > + fd_install(fd, file); > + get_file(file); > + } > + return fd; > +} What happens if another thread closes the descriptor in question between fd_install() and get_file()? > + fd = cr_attach_file(file); /* no need to cleanup 'file' below */ > + if (fd < 0) { > + filp_close(file, NULL); > + ret = fd; > + goto out; > + } > + > + /* register new tuple in hash table */ > + ret = cr_obj_add_ref(ctx, file, parent, CR_OBJ_FILE, 0); > + if (ret < 0) > + goto out; Who said that file still exists at that point? BTW, there are shitloads of races here - references to fd and struct file * are mixed in a way that breaks *badly* if descriptor table is played with by another thread. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org