linux-kernel - Re: [PATCH 2/6] md: dm-crypt: Set cc->iv

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Message-ID: <345bde7b-ac61-8265-8dce-d6a9dc1ca2fe@quicinc.com>
Date: Fri, 2 Aug 2024 09:51:44 +0530
From: Md Sadre Alam <quic_mdalam@...cinc.com>
To: Milan Broz <gmazyland@...il.com>, <axboe@...nel.dk>, <agk@...hat.com>,
        <snitzer@...nel.org>, <mpatocka@...hat.com>, <adrian.hunter@...el.com>,
        <quic_asutoshd@...cinc.com>, <ritesh.list@...il.com>,
        <ulf.hansson@...aro.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <dm-devel@...ts.linux.dev>,
        <linux-mmc@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <quic_viswanat@...cinc.com>, <quic_srichara@...cinc.com>,
        <quic_varada@...cinc.com>
Subject: Re: [PATCH 2/6] md: dm-crypt: Set cc->iv_size to 4 bytes



On 7/31/2024 6:11 PM, Milan Broz wrote:
> On 7/30/24 1:58 PM, Md Sadre Alam wrote:
>> Set cc->iv_size to 4 bytes instead of 8 bytes, since
>> this cc->iv_size is passing as data unit bytes to
>> blk_crypto_init_key(). Since CQHCI driver having
>> limitation for data unit bytes to 32-bit only.
> 
> In dm-crypt, plain64 IV is defined as "little-endian 64bit IV"
> and was introduced to fix security problem when 32bit "plain" IV
> overflows and IV is reused.
> 
> In that case you can move ciphertext sector between places with
> the same IV (but different offsets) and these will be still
> correctly decrypted.
> 
> If I understand it correctly, this reintroduces the same problem here.
> If you have 32bit only, just use "plain" and do not support plain64 here.
> 
> (In general, I do not understand why you are sending patches
> for dm-crypt code that is clearly not upstream.
> I hope this code will never be accepted.)

  Thanks for reviewing. As Mikulas suggested for
  new target driver for "inline-crypt". Will create
  new target driver and post it.

> 
> Milan
> 
>>
>> Signed-off-by: Md Sadre Alam <quic_mdalam@...cinc.com>
>> ---
>>   drivers/md/dm-crypt.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
>> index 37add222b169..c0257d961968 100644
>> --- a/drivers/md/dm-crypt.c
>> +++ b/drivers/md/dm-crypt.c
>> @@ -2490,7 +2490,7 @@ static int crypt_select_inline_crypt_mode(struct dm_target *ti, char *cipher,
>>       }
>>       if (ivmode == NULL || (strcmp(ivmode, "plain64") == 0)) {
>> -        cc->iv_size = 8;
>> +        cc->iv_size = 4;
>>       } else {
>>           ti->error = "Invalid IV mode for inline_crypt";
>>           return -EINVAL;
>