linux-hardening - Re: [PATCH] crypto: Use struct

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Date:   Wed, 18 May 2022 09:01:00 +0800
From:   "Guozihua (Scott)" <guozihua@...wei.com>
To:     Kees Cook <keescook@...omium.org>
CC:     <keyrings@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
        <davem@...emloft.net>, <dhowells@...hat.com>,
        <herbert@...dor.apana.org.au>, <gustavoars@...nel.org>,
        <linux-hardening@...r.kernel.org>
Subject: Re: [PATCH] crypto: Use struct_size() helper in kmalloc()

On 2022/5/18 5:26, Kees Cook wrote:
> On Tue, May 17, 2022 at 04:05:32PM +0800, GUO Zihua wrote:
>> Make use of struct_size() heler for structures containing flexible array
>> member instead of sizeof() which prevents potential issues as well as
>> addressing the following sparse warning:
>>
>> crypto/asymmetric_keys/asymmetric_type.c:155:23: warning: using sizeof
>> on a flexible structure
>> crypto/asymmetric_keys/asymmetric_type.c:247:28: warning: using sizeof
>> on a flexible structure
>>
>> Reference: https://github.com/KSPP/linux/issues/174
>>
>> Signed-off-by: GUO Zihua <guozihua@...wei.com>
>> ---
>>   crypto/asymmetric_keys/asymmetric_type.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
>> index 41a2f0eb4ce4..96a99a91bf17 100644
>> --- a/crypto/asymmetric_keys/asymmetric_type.c
>> +++ b/crypto/asymmetric_keys/asymmetric_type.c
>> @@ -152,7 +152,7 @@ struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
>>   {
>>   	struct asymmetric_key_id *kid;
>>   
>> -	kid = kmalloc(sizeof(struct asymmetric_key_id) + len_1 + len_2,
>> +	kid = kmalloc(struct_size(kid, data, len_1 + len_2),
> 
> Please use the size_add() helper for this open-coded add here.
> 
>>   		      GFP_KERNEL);
>>   	if (!kid)
>>   		return ERR_PTR(-ENOMEM);
>> @@ -244,7 +244,7 @@ struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
>>   	if (asciihexlen & 1)
>>   		return ERR_PTR(-EINVAL);
>>   
>> -	match_id = kmalloc(sizeof(struct asymmetric_key_id) + asciihexlen / 2,
>> +	match_id = kmalloc(struct_size(match_id, data, asciihexlen / 2),
> 
> There is no size_div(), but that's ok here because the denominator is an
> constant expression.
> 
>>   			   GFP_KERNEL);
>>   	if (!match_id)
>>   		return ERR_PTR(-ENOMEM);
>> -- 
>> 2.36.0
>>
> 

Thanks Kees,

A v2 patch has been submitted.

-- 
Best
GUO Zihua