From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761630Ab3DDOWy (ORCPT ); Thu, 4 Apr 2013 10:22:54 -0400 Received: from mail-pd0-f180.google.com ([209.85.192.180]:57630 "EHLO mail-pd0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761439Ab3DDOWx (ORCPT ); Thu, 4 Apr 2013 10:22:53 -0400 From: Ming Lei To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Ming Lei , Dave Jones , Sasha Levin Subject: [PATCH v1] sysfs: check if one entry has been removed before freeing Date: Thu, 4 Apr 2013 22:22:37 +0800 Message-Id: <1365085357-15268-1-git-send-email-ming.lei@canonical.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It might be a kernel disaster if one sysfs entry is freed but still referenced by sysfs tree. Recently Dave and Sasha reported one use-after-free problem on sysfs entry, and the problem has been troubleshooted with help of debug message added in this patch. Given sysfs_get_dirent/sysfs_put are exported APIs, even inside sysfs they are called in many contexts(kobject/attribe add/delete, inode init/drop, dentry lookup/release, readdir, ...), it is healthful to check the removed flag before freeing one entry and dump message if it is freeing without being removed first. Cc: Dave Jones Cc: Sasha Levin Signed-off-by: Ming Lei --- v1: - use WARN() instead of BUG() as suggested by Dave and Greg fs/sysfs/dir.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 1bf016b..e8e0e71 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -268,6 +268,10 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) */ parent_sd = sd->s_parent; + WARN(!(sd->s_flags & SYSFS_FLAG_REMOVED), + "sysfs: free using entry: %s/%s\n", + parent_sd ? parent_sd->s_name : "", sd->s_name); + if (sysfs_type(sd) == SYSFS_KOBJ_LINK) sysfs_put(sd->s_symlink.target_sd); if (sysfs_type(sd) & SYSFS_COPY_NAME) @@ -386,7 +390,7 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) sd->s_name = name; sd->s_mode = mode; - sd->s_flags = type; + sd->s_flags = type | SYSFS_FLAG_REMOVED; return sd; @@ -466,6 +470,9 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd) ps_iattrs->ia_ctime = ps_iattrs->ia_mtime = CURRENT_TIME; } + /* Mark the entry added into directory tree */ + sd->s_flags &= ~SYSFS_FLAG_REMOVED; + return 0; } -- 1.7.9.5