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

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Date:   Wed, 12 Jul 2023 18:04:57 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Yu Kuai <yukuai1@...weicloud.com>,
        Sergei Shtepa <sergei.shtepa@...am.com>, axboe@...nel.dk,
        hch@...radead.org, corbet@....net, snitzer@...nel.org
Cc:     viro@...iv.linux.org.uk, brauner@...nel.org, dchinner@...hat.com,
        willy@...radead.org, dlemoal@...nel.org, linux@...ssschuh.net,
        jack@...e.cz, ming.lei@...hat.com, linux-block@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        Donald Buczek <buczek@...gen.mpg.de>,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v5 02/11] block: Block Device Filtering Mechanism

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().

Thanks,
Kuai