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 <davej@redhat.com>
Tested-by: Sasha Levin <levinsasha928@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 2fbdff6..c9e1660 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -1058,10 +1058,21 @@
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,
};
