From 76bfc5ab57137d351a9046a002ee39a220d0e012 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Wed, 20 Mar 2013 23:25:24 +0800 Subject: sysfs: fix race between readdir and lseek commit 991f76f837bf22c5bb07261cfd86525a0a96650c upstream. While readdir() is running, lseek() may set filp->f_pos as zero, then may leave filp->private_data pointing to one sysfs_dirent object without holding its reference counter, so the sysfs_dirent object may be used after free in next readdir(). This patch holds inode->i_mutex to avoid the problem since the lock is always held in readdir path. Reported-by: Dave Jones Tested-by: Sasha Levin Signed-off-by: Ming Lei Signed-off-by: Greg Kroah-Hartman [bwh: Backported to 3.2: open-code file_inode() which we don't have] Signed-off-by: Ben Hutchings --- fs/sysfs/dir.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'fs/sysfs') diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index fabbb81f5ce4..309d21ad21fa 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -1023,10 +1023,21 @@ static int sysfs_readdir(struct file * filp, void * dirent, filldir_t filldir) return 0; } +static loff_t sysfs_dir_llseek(struct file *file, loff_t offset, int whence) +{ + struct inode *inode = file->f_path.dentry->d_inode; + loff_t ret; + + mutex_lock(&inode->i_mutex); + ret = generic_file_llseek(file, offset, whence); + mutex_unlock(&inode->i_mutex); + + return ret; +} const struct file_operations sysfs_dir_operations = { .read = generic_read_dir, .readdir = sysfs_readdir, .release = sysfs_dir_release, - .llseek = generic_file_llseek, + .llseek = sysfs_dir_llseek, }; -- cgit v1.2.3