From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751882AbZKOGvv (ORCPT ); Sun, 15 Nov 2009 01:51:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751820AbZKOGvu (ORCPT ); Sun, 15 Nov 2009 01:51:50 -0500 Received: from tomts16-srv.bellnexxia.net ([209.226.175.4]:53803 "EHLO tomts16-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751819AbZKOGvu (ORCPT ); Sun, 15 Nov 2009 01:51:50 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ApsEAD8u/0pGGN1W/2dsb2JhbACBTNA3hDwE Date: Sun, 15 Nov 2009 01:51:53 -0500 From: Mathieu Desnoyers To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org Subject: [PATCH] Debugfs: fix create mutex racy fops and private data Message-ID: <20091115065153.GA29928@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 01:50:07 up 88 days, 17:39, 4 users, load average: 0.72, 0.33, 0.19 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Setting fops and private data outside of the mutex at debugfs file creation introduces a race where the files can be opened with the wrong file operations and private data. It is easy to trigger with a process waiting on file creation notification. Signed-off-by: Mathieu Desnoyers CC: Greg Kroah-Hartman --- fs/debugfs/inode.c | 55 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 32 insertions(+), 23 deletions(-) Index: linux-2.6-lttng/fs/debugfs/inode.c =================================================================== --- linux-2.6-lttng.orig/fs/debugfs/inode.c 2009-11-15 01:22:59.000000000 -0500 +++ linux-2.6-lttng/fs/debugfs/inode.c 2009-11-15 01:42:46.000000000 -0500 @@ -32,7 +32,9 @@ static struct vfsmount *debugfs_mount; static int debugfs_mount_count; static bool debugfs_registered; -static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev) +static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev, + void *data, const struct file_operations *fops) + { struct inode *inode = new_inode(sb); @@ -44,14 +46,18 @@ static struct inode *debugfs_get_inode(s init_special_inode(inode, mode, dev); break; case S_IFREG: - inode->i_fop = &debugfs_file_operations; + inode->i_fop = fops ? fops : &debugfs_file_operations; + inode->i_private = data; break; case S_IFLNK: inode->i_op = &debugfs_link_operations; + inode->i_fop = fops; + inode->i_private = data; break; case S_IFDIR: inode->i_op = &simple_dir_inode_operations; - inode->i_fop = &simple_dir_operations; + inode->i_fop = fops ? fops : &simple_dir_operations; + inode->i_private = data; /* directory inodes start off with i_nlink == 2 * (for "." entry) */ @@ -64,7 +70,8 @@ static struct inode *debugfs_get_inode(s /* SMP-safe */ static int debugfs_mknod(struct inode *dir, struct dentry *dentry, - int mode, dev_t dev) + int mode, dev_t dev, void *data, + const struct file_operations *fops) { struct inode *inode; int error = -EPERM; @@ -72,7 +79,7 @@ static int debugfs_mknod(struct inode *d if (dentry->d_inode) return -EEXIST; - inode = debugfs_get_inode(dir->i_sb, mode, dev); + inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops); if (inode) { d_instantiate(dentry, inode); dget(dentry); @@ -81,12 +88,13 @@ static int debugfs_mknod(struct inode *d return error; } -static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode) +static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode, + void *data, const struct file_operations *fops) { int res; mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR; - res = debugfs_mknod(dir, dentry, mode, 0); + res = debugfs_mknod(dir, dentry, mode, 0, data, fops); if (!res) { inc_nlink(dir); fsnotify_mkdir(dir, dentry); @@ -94,18 +102,20 @@ static int debugfs_mkdir(struct inode *d return res; } -static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode) +static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode, + void *data, const struct file_operations *fops) { mode = (mode & S_IALLUGO) | S_IFLNK; - return debugfs_mknod(dir, dentry, mode, 0); + return debugfs_mknod(dir, dentry, mode, 0, data, fops); } -static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode) +static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode, + void *data, const struct file_operations *fops) { int res; mode = (mode & S_IALLUGO) | S_IFREG; - res = debugfs_mknod(dir, dentry, mode, 0); + res = debugfs_mknod(dir, dentry, mode, 0, data, fops); if (!res) fsnotify_create(dir, dentry); return res; @@ -139,7 +149,9 @@ static struct file_system_type debug_fs_ static int debugfs_create_by_name(const char *name, mode_t mode, struct dentry *parent, - struct dentry **dentry) + struct dentry **dentry, + void *data, + const struct file_operations *fops) { int error = 0; @@ -164,13 +176,16 @@ static int debugfs_create_by_name(const if (!IS_ERR(*dentry)) { switch (mode & S_IFMT) { case S_IFDIR: - error = debugfs_mkdir(parent->d_inode, *dentry, mode); + error = debugfs_mkdir(parent->d_inode, *dentry, mode, + data, fops); break; case S_IFLNK: - error = debugfs_link(parent->d_inode, *dentry, mode); + error = debugfs_link(parent->d_inode, *dentry, mode, + data, fops); break; default: - error = debugfs_create(parent->d_inode, *dentry, mode); + error = debugfs_create(parent->d_inode, *dentry, mode, + data, fops); break; } dput(*dentry); @@ -221,19 +236,13 @@ struct dentry *debugfs_create_file(const if (error) goto exit; - error = debugfs_create_by_name(name, mode, parent, &dentry); + error = debugfs_create_by_name(name, mode, parent, &dentry, + data, fops); if (error) { dentry = NULL; simple_release_fs(&debugfs_mount, &debugfs_mount_count); goto exit; } - - if (dentry->d_inode) { - if (data) - dentry->d_inode->i_private = data; - if (fops) - dentry->d_inode->i_fop = fops; - } exit: return dentry; } -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68