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
Git-commit: 6b136a24b05c81a24e0b648a4bd938bcd0c4f69e
Patch-mainline: v4.16-rc1
References: bsc#1104967,FATE#325924
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>
Acked-by: Hannes Reinecke <hare@suse.com>
---
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 fa31ceaa8de6..21cbc1f071c6 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);
--
2.16.4