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

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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>
This commit is contained in:
Eryu Guan 2018-01-24 01:20:00 +08:00 committed by Jens Axboe
parent 20d59023c5
commit 6b136a24b0
1 changed files with 5 additions and 1 deletions
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6
block/blk-mq-debugfs.c
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@ -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);