linux-kernel - Re: [PATCH] crypto: fix uninit-value in af_alg_free

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Date:   Mon, 14 Aug 2023 21:04:15 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     David Howells <dhowells@...hat.com>
Cc:     herbert@...dor.apana.org.au, davem@...emloft.net,
        pabeni@...hat.com, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+cba21d50095623218389@...kaller.appspotmail.com
Subject: Re: [PATCH] crypto: fix uninit-value in af_alg_free_resources

Hi David,

David Howells <dhowells@...hat.com> says:
> Pavel Skripkin <paskripkin@...il.com> wrote:
> 
>> Syzbot was able to trigger use of uninitialized memory in
>> af_alg_free_resources.
>> 
>> Bug is caused by missing initialization of rsgl->sgl.need_unpin before
>> adding to rsgl_list. Then in case of extract_iter_to_sg() failure, rsgl
>> is left with uninitialized need_unpin which is read during clean up
> 
> Looks feasible :-).
> 
>> +		rsgl->sgl.need_unpin = 0;
>> +
> 
> The blank line isn't really necessary and it's a bool, so can you use 'false'
> rather than '0'?
> 
> Alternatively, it might be better to move:
> 
> 		rsgl->sgl.need_unpin =
> 			iov_iter_extract_will_pin(&msg->msg_iter);
> 
> up instead.
> 

Thank you for review! I've just posted v2 :)



With regards,
Pavel Skripkin