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

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Message-ID: <20200804040420.GA10850@gondor.apana.org.au>
Date:   Tue, 4 Aug 2020 14:04:20 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Liwei Song <liwei.song@...driver.com>
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 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.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt