linux-kernel - Re: [PATCH] dm verity: fix no salt used use case

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Date:   Thu, 18 May 2017 13:03:06 +0200
From:   Milan Broz <gmazyland@...il.com>
To:     Gilad Ben-Yossef <gilad@...yossef.com>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com,
        Shaohua Li <shli@...nel.org>
Cc:     Marian Csontos <mcsontos@...hat.com>, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dm verity: fix no salt used use case


On 05/18/2017 12:47 PM, Gilad Ben-Yossef wrote:
> DM-Verity has an (undocumented) mode where no salt is used.
> This was never handled directly by the DM-Verity code, instead working due
> to the fact that calling crypto_shash_update() with a zero length data is
> an implicit noop.
> 
> This is no longer the case now that we have switched to
> crypto_ahash_update(). Fix the issue by introducing an explicit handling
> of the no salt use case to DM-Verity.
> 
> Signed-off-by: Gilad Ben-Yossef <gilad@...yossef.com>
> Reported-by: Marian Csontos <mcsontos@...hat.com>
> Fixes: d1ac3ff ("dm verity: switch to using asynchronous hash crypto API")
> CC: Milan Broz <gmazyland@...il.com>

Tested-by: Milan Broz <gmazyland@...il.com>

Thanks for quick fix!

Mike: this must go to 4.12rc (only).

m.


> ---
>  drivers/md/dm-verity-target.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
> index 97de961..1ec9b2c 100644
> --- a/drivers/md/dm-verity-target.c
> +++ b/drivers/md/dm-verity-target.c
> @@ -166,7 +166,7 @@ static int verity_hash_init(struct dm_verity *v, struct ahash_request *req,
>  		return r;
>  	}
>  
> -	if (likely(v->version >= 1))
> +	if (likely(v->salt_size && (v->version >= 1)))
>  		r = verity_hash_update(v, req, v->salt, v->salt_size, res);
>  
>  	return r;
> @@ -177,7 +177,7 @@ static int verity_hash_final(struct dm_verity *v, struct ahash_request *req,
>  {
>  	int r;
>  
> -	if (unlikely(!v->version)) {
> +	if (unlikely(v->salt_size && (!v->version))) {
>  		r = verity_hash_update(v, req, v->salt, v->salt_size, res);
>  
>  		if (r < 0) {
>