From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753142AbZHXRjF (ORCPT ); Mon, 24 Aug 2009 13:39:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753087AbZHXRjB (ORCPT ); Mon, 24 Aug 2009 13:39:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45022 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753081AbZHXRi7 (ORCPT ); Mon, 24 Aug 2009 13:38:59 -0400 From: Eric Paris Subject: [PATCH 3/3] inotify: fix locking around inotify watching in the idr To: linux-kernel@vger.kernel.org, linux-fs-devel@vger.kernel.org Cc: zdenek.kabelac@gmail.com, torvalds@linux-foundation.org, christoph.thielecke@gmx.de, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, grant.wilson@zen.co.uk, mikko.cal@gmail.com Date: Mon, 24 Aug 2009 13:38:21 -0400 Message-ID: <20090824173821.14196.80746.stgit@paris.rdu.redhat.com> In-Reply-To: <20090824173524.14196.25992.stgit@paris.rdu.redhat.com> References: <20090824173524.14196.25992.stgit@paris.rdu.redhat.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The are races around the idr storage of inotify watches. It's possible that a watch could be found from sys_inotify_rm_watch() in the idr, but it could be removed from the idr before that code does it's removal. Move the locking and the refcnt'ing so that these have to happen atomically. Signed-off-by: Eric Paris --- fs/notify/inotify/inotify_user.c | 51 +++++++++++++++++++++++++++++++------- 1 files changed, 41 insertions(+), 10 deletions(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index d8f73c2..c0ed0aa 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -364,20 +364,54 @@ static int inotify_find_inode(const char __user *dirname, struct path *path, uns return error; } +/* + * Remove the mark from the idr (if present) and drop the reference + * on the mark because it was in the idr. + */ static void inotify_remove_from_idr(struct fsnotify_group *group, struct inotify_inode_mark_entry *ientry) { struct idr *idr; + struct fsnotify_mark_entry *entry; + struct inotify_inode_mark_entry *found_ientry; + int wd; spin_lock(&group->inotify_data.idr_lock); idr = &group->inotify_data.idr; - idr_remove(idr, ientry->wd); - spin_unlock(&group->inotify_data.idr_lock); + wd = ientry->wd; + + if (wd == -1) + goto out; + + entry = idr_find(&group->inotify_data.idr, wd); + if (unlikely(!entry)) + goto out; + + found_ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry); + if (unlikely(found_ientry != ientry)) { + /* We found an entry in the idr with the right wd, but it's + * not the entry we were told to remove. eparis seriously + * fucked up somewhere. */ + WARN_ON(1); + ientry->wd = -1; + goto out; + } + + /* There better be at least one ref for being in the idr and one + * reference from whatever called us. */ + BUG_ON(atomic_read(&entry->refcnt) < 2); + + idr_remove(idr, wd); ientry->wd = -1; + + /* removed from the idr, drop that ref */ + fsnotify_put_mark(entry); +out: + spin_unlock(&group->inotify_data.idr_lock); } + /* - * Send IN_IGNORED for this wd, remove this wd from the idr, and drop the - * internal reference help on the mark because it is in the idr. + * Send IN_IGNORED for this wd, remove this wd from the idr. */ void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry *entry, struct fsnotify_group *group) @@ -417,9 +451,6 @@ skip_send_ignore: /* remove this entry from the idr */ inotify_remove_from_idr(group, ientry); - /* removed from idr, drop that reference */ - fsnotify_put_mark(entry); - atomic_dec(&group->inotify_data.user->inotify_watches); } @@ -535,6 +566,9 @@ retry: goto out_err; } + /* we put the mark on the idr, take a reference */ + fsnotify_get_mark(&tmp_ientry->fsn_entry); + /* we are on the idr, now get on the inode */ ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode); if (ret) { @@ -543,9 +577,6 @@ retry: goto out_err; } - /* we put the mark on the idr, take a reference */ - fsnotify_get_mark(&tmp_ientry->fsn_entry); - /* update the idr hint, who cares about races, it's just a hint */ group->inotify_data.last_wd = tmp_ientry->wd;