4.14-stable review patch. If anyone has any objections, please let me know.
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From: Eryu Guan eguan@redhat.com
[ 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@redhat.com Signed-off-by: Eryu Guan eguan@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-mq-debugfs.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -704,7 +704,11 @@ static ssize_t blk_mq_debugfs_write(stru 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);