From: Pavel Begunkov <[email protected]>
To: "Zhang, Qiang" <[email protected]>,
Hillf Danton <[email protected]>,
"[email protected]" <[email protected]>
Cc: "[email protected]"
<[email protected]>,
"[email protected]" <[email protected]>,
"[email protected]" <[email protected]>
Subject: Re: 回复: [PATCH] io-wq: Fix UAF when wakeup wqe in hash waitqueue
Date: Mon, 24 May 2021 11:16:40 +0100 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <DM6PR11MB4202B442C4C27740B6EE2D64FF269@DM6PR11MB4202.namprd11.prod.outlook.com>
On 5/24/21 10:19 AM, Zhang, Qiang wrote:
[...]
>> Scratch scalp one inch off to work out how this is a cure given a) uaf makes
>> no sense without free and b) how io workers could survive
>> wait_for_completion(&wq->worker_done).
>>
>> If they could OTOH then this is not the pill for the leak in worker_refs.
>
> Hello Pavel Begunkov, Hillf Danton
>
> Sorry there is a problem with the calltrace described in my message. Please ignore this modification
Haven't looked at the trace and description, but I do think
there is a problem it solves.
1) io_wait_on_hash() -> __add_wait_queue(&hash->wait, &wqe->wait);
2) (note: wqe is a worker) wqe's workers exit dropping refs
3) refs are zero, free io-wq
4) @hash is shared, so other task/wq does wake_up(&wq->hash->wait);
5) it wakes freed wqe
step 4) is a bit more trickier than that, tl;dr;
wq3:worker1 | locks bit1
wq1:worker2 | waits bit1
wq2:worker1 | waits bit1
wq1:worker3 | waits bit1
wq3:worker1 | drop bit1
wq1:worker2 | locks bit1
wq1:worker2 | completes all wq1 bit1 work items
wq1:worker2 | drop bit1, exit and free io-wq
wq2:worker1 | locks bit1
wq1 | free complete
wq2:worker1 | drops bit1
wq1:worker3 | waked up, even though freed
Can be simplified, don't want to waste time on that
--
Pavel Begunkov
next prev parent reply other threads:[~2021-05-24 10:16 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-24 7:18 [PATCH] io-wq: Fix UAF when wakeup wqe in hash waitqueue qiang.zhang
[not found] ` <[email protected]>
2021-05-24 9:19 ` 回复: " Zhang, Qiang
2021-05-24 10:16 ` Pavel Begunkov [this message]
2021-05-25 2:01 ` 回复: " Zhang, Qiang
2021-06-07 17:38 ` Pavel Begunkov
2021-06-10 1:49 ` Zhang, Qiang
2021-05-24 10:18 ` Pavel Begunkov
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