Re: [PATCH v5 02/11] block: Block Device Filtering Mechanism

Yu Kuai
2023-07-12T12:35:06Z

Hi,

在 2023/07/12 18:04, Yu Kuai 写道:
> Hi,
>
> 在 2023/07/11 10:02, Yu Kuai 写道:
>
>>> +static bool submit_bio_filter(struct bio *bio)
>>> +{
>>> +    if (bio_flagged(bio, BIO_FILTERED))
>>> +        return false;
>>> +
>>> +    bio_set_flag(bio, BIO_FILTERED);
>>> +    return bio->bi_bdev->bd_filter->ops->submit_bio(bio);
>>> +}
>>> +
>>>   static void __submit_bio(struct bio *bio)
>>>   {
>>> +    /*
>>> +     * If there is a filter driver attached, check if the BIO needs
>>> to go to
>>> +     * the filter driver first, which can then pass on the bio or
>>> consume it.
>>> +     */
>>> +    if (bio->bi_bdev->bd_filter && submit_bio_filter(bio))
>>> +        return;
>>> +
>>>       if (unlikely(!blk_crypto_bio_prep(&bio)))
>>>           return;
>
> ...
>
>>> +static void __blkfilter_detach(struct block_device *bdev)
>>> +{
>>> +    struct blkfilter *flt = bdev->bd_filter;
>>> +    const struct blkfilter_operations *ops = flt->ops;
>>> +
>>> +    bdev->bd_filter = NULL;
>>> +    ops->detach(flt);
>>> +    module_put(ops->owner);
>>> +}
>>> +
>>> +void blkfilter_detach(struct block_device *bdev)
>>> +{
>>> +    if (bdev->bd_filter) {
>>> +        blk_mq_freeze_queue(bdev->bd_queue);
>
> And this is not sate as well, for bio-based device, q_usage_counter is
> not grabbed while submit_bio_filter() is called, hence there is a risk
> of uaf from submit_bio_filter().

And there is another question, can blkfilter_detach() from
del_gendisk/delete_partiton and ioctl concurrent? I think it's a
problem.

Thanks,
Kuai
>
> Thanks,
> Kuai
>
> .
>