From: Eryu Guan <eguan@xxxxxxxxxx> [ Upstream commit 6b136a24b05c81a24e0b648a4bd938bcd0c4f69e ] Attributes that only implement .seq_ops are read-only, any write to them should be rejected. But currently kernel would crash when writing to such debugfs entries, e.g. chmod +w /sys/kernel/debug/block/<dev>/requeue_list echo 0 > /sys/kernel/debug/block/<dev>/requeue_list chmod -w /sys/kernel/debug/block/<dev>/requeue_list Fix it by returning -EPERM in blk_mq_debugfs_write() when writing to such attributes. Cc: Ming Lei <ming.lei@xxxxxxxxxx> Signed-off-by: Eryu Guan <eguan@xxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- block/blk-mq-debugfs.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index b56a4f35720d..54bd8c31b822 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -703,7 +703,11 @@ static ssize_t blk_mq_debugfs_write(struct file *file, const char __user *buf, const struct blk_mq_debugfs_attr *attr = m->private; void *data = d_inode(file->f_path.dentry->d_parent)->i_private; - if (!attr->write) + /* + * Attributes that only implement .seq_ops are read-only and 'attr' is + * the same with 'data' in this case. + */ + if (attr == data || !attr->write) return -EPERM; return attr->write(data, buf, count, ppos); -- 2.15.1