linux-kernel - Re: [PATCH] block, bfq: fix uaf for bfqq in bic_set

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Message-ID: <7ae20fa2-d9b4-9e21-4209-81bf4845a3c5@kernel.dk>
Date:   Sun, 29 Jan 2023 14:51:38 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Yu Kuai <yukuai1@...weicloud.com>, jack@...e.cz, tj@...nel.org,
        josef@...icpanda.com, paolo.valente@...aro.org,
        shinichiro.kawasaki@....com
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] block, bfq: fix uaf for bfqq in bic_set_bfqq()

On 1/28/23 6:38 PM, Yu Kuai wrote:
> Hi, Jens
> 
> 在 2023/01/13 17:44, Yu Kuai 写道:
>> After commit 64dc8c732f5c ("block, bfq: fix possible uaf for 'bfqq->bic'"),
>> bic->bfqq will be accessed in bic_set_bfqq(), however, in some context
>> bic->bfqq will be freed first, and bic_set_bfqq() is called with the freed
>> bic->bfqq.
>>
>> Fix the problem by always freeing bfqq after bic_set_bfqq().
>>
> 
> Sorry that I send this patch will wrong email, and you might missed this
> patch.
> 
> Can you apply this patch? This patch can't be applied directly to lower
> version due to Paolo's patchset, I'll send lts patch seperately.

I'm confused... So this patch only applies to the 6.3 branch, yet we
need it in 6.2 as far as I can tell. Why isn't it against block-6.2
then?

-- 
Jens Axboe