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