Commit 6b136a24 authored Jan 24, 2018 by Eryu Guan Committed by Jens Axboe Jan 24, 2018

blk-mq-debugfs: don't allow write on attributes with seq_operations set



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@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 20d59023

block/blk-mq-debugfs.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -697,7 +697,11 @@ 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);

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