From 6b136a24b05c81a24e0b648a4bd938bcd0c4f69e Mon Sep 17 00:00:00 2001 From: Eryu Guan <eguan@redhat.com> Date: Wed, 24 Jan 2018 01:20:00 +0800 Subject: [PATCH] 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> --- 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 fa31ceaa8de6c..21cbc1f071c65 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -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); -- GitLab