Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH block/for-linus] blkcg: Fix multiple bugs in
 blkcg_activate_policy()
To:     Tejun Heo <tj@kernel.org>
Cc:     Julia Lawall <julia.lawall@lip6.fr>, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com,
        linux-block@vger.kernel.org
References: <alpine.DEB.2.21.1910151232480.2818@hadrien>
 <20191015154827.GK18794@devbig004.ftw2.facebook.com>
 <07cbc404-65db-b236-9ae2-558197b8cdb6@kernel.dk>
 <20191015160347.GM18794@devbig004.ftw2.facebook.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <8406cdae-fa26-3db5-f97d-347059cdbc16@kernel.dk>
Date:   Tue, 15 Oct 2019 10:13:38 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.9.0
MIME-Version: 1.0
In-Reply-To: <20191015160347.GM18794@devbig004.ftw2.facebook.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 10/15/19 10:03 AM, Tejun Heo wrote:
> blkcg_activate_policy() has the following bugs.
> 
> * cf09a8ee19ad ("blkcg: pass @q and @blkcg into
>    blkcg_pol_alloc_pd_fn()") added @blkcg to ->pd_alloc_fn(); however,
>    blkcg_activate_policy() ends up using pd's allocated for the root
>    blkcg for all preallocations, so ->pd_init_fn() for non-root blkcgs
>    can be passed in pd's which are allocated for the root blkcg.
> 
>    For blk-iocost, this means that ->pd_init_fn() can write beyond the
>    end of the allocated object as it determines the length of the flex
>    array at the end based on the blkcg's nesting level.
> 
> * Each pd is initialized as they get allocated.  If alloc fails, the
>    policy will get freed with pd's initialized on it.
> 
> * After the above partial failure, the partial pds are not freed.
> 
> This patch fixes all the above issues by
> 
> * Restructuring blkcg_activate_policy() so that alloc and init passes
>    are separate.  Init takes place only after all allocs succeeded and
>    on failure all allocated pds are freed.
> 
> * Unifying and fixing the cleanup of the remaining pd_prealloc.

Great thanks, applied.

-- 
Jens Axboe