From: Ming Lei Date: Wed, 20 Mar 2013 15:25:24 +0000 (+0800) Subject: sysfs: fix race between readdir and lseek X-Git-Tag: firefly_0821_release~3680^2~826^2~1 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=991f76f837bf22c5bb07261cfd86525a0a96650c;p=firefly-linux-kernel-4.4.55.git sysfs: fix race between readdir and lseek 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 Cc: Signed-off-by: Ming Lei Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 2fbdff6be25c..c9e16608f486 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -1058,10 +1058,21 @@ 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_inode(file); + 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, };