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Thu, 06 Aug 2026 09:07:59 -0700 (PDT) Message-ID: Date: Fri, 7 Aug 2026 00:07:56 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.1.y] Fix memory leak in io_wq_create() on success path To: Greg KH Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260806142314.557312-1-shinnkka1@gmail.com> <2026080644-suffix-earthy-2f30@gregkh> <2026080636-financial-iron-4bd9@gregkh> Content-Language: en-US From: Chen Xiaokun In-Reply-To: <2026080636-financial-iron-4bd9@gregkh> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/8/6 23:29, Greg KH 写道: > On Thu, Aug 06, 2026 at 10:47:02PM +0800, xk c wrote: >> Greg KH 于2026年8月6日周四 22:33写道： >>> On Thu, Aug 06, 2026 at 10:23:14PM +0800, Chen Xiaokun wrote: >>>> The commit 657ca82526d0 introduced a temporary allowed_mask cpumask in >>>> io_wq_create(), which was freed only on the error path. This caused a >>>> memory leak of cpumask_size() bytes on every successful io_wq_create(). >>>> >>>> Fixes: 657ca82526d0 ("io_uring/io-wq: inherit cpuset of cgroup in io worker") >>>> Signed-off-by: Chen Xiaokun >>>> --- >>>> io_uring/io-wq.c | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c >>>> index 66fdd69fd6cb..34a1a9067cc2 100644 >>>> --- a/io_uring/io-wq.c >>>> +++ b/io_uring/io-wq.c >>>> @@ -1218,6 +1218,7 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data) >>>> wq->task = get_task_struct(data->task); >>>> atomic_set(&wq->worker_refs, 1); >>>> init_completion(&wq->worker_done); >>>> + free_cpumask_var(allowed_mask); >>>> return wq; >>>> err: >>>> io_wq_put_hash(data->hash); >>>> -- >>>> 2.55.0 >>>> >>>> >>> Why is this a stable-only patch? Was the backport wrong? Or is this >>> also in Linus's tree? >>> >> Linus's tree has not this issue. > You need to explain why, in great detail, Linus's tree does not have > this problem in the changelog. > > For example, try answering the questions I asked here, that should > provide you a framework for what to write. > > thnanks, This is a stable-only patch because the backport introduced a temporary allowed_mask variable without freeing it on the success path.  In Linus's tree, it is bound to wq, so there is no memory leak. > greg k-h > > Thanks for your patience, Chen