linux-kernel - Re: [PATCH] crypto: ccp - zero the cmd data after use it

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Date:   Tue, 4 Aug 2020 12:20:21 +0800
From:   Liwei Song <liwei.song@...driver.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
CC:     Tom Lendacky <thomas.lendacky@....com>,
        Gary Hook <gary.hook@....com>, David <davem@...emloft.net>,
        <linux-crypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: ccp - zero the cmd data after use it



On 8/4/20 12:04, Herbert Xu wrote:
> On Tue, Aug 04, 2020 at 11:51:47AM +0800, Liwei Song wrote:
>>
>> On 8/3/20 20:52, Herbert Xu wrote:
>>> On Mon, Aug 03, 2020 at 03:58:58PM +0800, Liwei Song wrote:
>>>> exist the following assignment in ccp(ignore the force
>>>> convert of the struct) by list_del in ccp_dequeue_cmd():
>>>> req->__ctx->cmd->entry->next = LIST_POISON1;
>>>>
>>>> after use the req, kzfree(req) can not zero the entry
>>>> entry->next = LIST_POISON1 of the ccp_cmd(cmd) struct
>>>> when this address available as slub freelist pointer, this will cause
>>>> the following "general protection fault" error if some process meet
>>>> this LIST_POISON1 value address when request memory:
>>>
>>> Your description makes no sense.  Please rewrite it and explain
>>> the problem properly.
>>
>> The problem here is that the entry of struct ccp_cmd is not zeroed after we use it,
>> If the other process got this address by kmalloc(), this illegal value "LIST_POISON1"
>> will cause "general protection fault" error.
> 
> If that's the case surely the other process should be zeroing
> the memory? Your explanation still makes no sense.

Yes, the other process should do this zero work, but the case I met is
this address will appear in the slab_alloc_node() as freelist pointer of slub,
and before slub do zero wrok, even kzalloc() doesn't work with this address.

Thanks,
Liwei.


> 
> Thanks,
>