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Subject: Re: [PATCH] crypto: ccp - zero the cmd data after use it
To:     Herbert Xu <herbert@gondor.apana.org.au>
CC:     Tom Lendacky <thomas.lendacky@amd.com>,
        Gary Hook <gary.hook@amd.com>, David <davem@davemloft.net>,
        <linux-crypto@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20200803075858.3561-1-liwei.song@windriver.com>
 <20200803125242.GA7689@gondor.apana.org.au>
 <87ae939b-4983-4e96-cc3d-1aa1d1b3d3ae@windriver.com>
 <20200804040420.GA10850@gondor.apana.org.au>
From:   Liwei Song <liwei.song@windriver.com>
Message-ID: <1b6be879-8449-b519-046f-0312e57aa9a4@windriver.com>
Date:   Tue, 4 Aug 2020 12:20:21 +0800
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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,
>