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From: Paolo Bonzini <pbonzini@redhat.com>
To: Heiko Carstens <heiko.carstens@de.ibm.com>,
	SF Markus Elfring <elfring@users.sourceforge.net>
Cc: linux-s390@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Michael Holzheu <holzheu@linux.vnet.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org,
	Julia Lawall <julia.lawall@lip6.fr>
Subject: Re: [PATCH] s390/hypfs: Use kmalloc_array() in diag0c_store()
Date: Thu, 1 Sep 2016 17:39:02 +0200	[thread overview]
Message-ID: <a5ade28e-c2d3-2727-ee63-b2e285a7f316@redhat.com> (raw)
In-Reply-To: <20160901103245.GA3624@osiris>



On 01/09/2016 12:32, Heiko Carstens wrote:
> On Thu, Sep 01, 2016 at 11:38:15AM +0200, SF Markus Elfring wrote:
>> From: Markus Elfring <elfring@users.sourceforge.net>
>> Date: Thu, 1 Sep 2016 11:30:58 +0200
>>
>> A multiplication for the size determination of a memory allocation
>> indicated that an array data structure should be processed.
>> Thus use the corresponding function "kmalloc_array".
>>
>> This issue was detected by using the Coccinelle software.
>>
>> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
>> ---
>>  arch/s390/hypfs/hypfs_diag0c.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/hypfs/hypfs_diag0c.c b/arch/s390/hypfs/hypfs_diag0c.c
>> index 0f1927c..61418a8 100644
>> --- a/arch/s390/hypfs/hypfs_diag0c.c
>> +++ b/arch/s390/hypfs/hypfs_diag0c.c
>> @@ -48,7 +48,9 @@ static void *diag0c_store(unsigned int *count)
>>  
>>  	get_online_cpus();
>>  	cpu_count = num_online_cpus();
>> -	cpu_vec = kmalloc(sizeof(*cpu_vec) * num_possible_cpus(), GFP_KERNEL);
>> +	cpu_vec = kmalloc_array(num_possible_cpus(),
>> +				sizeof(*cpu_vec),
>> +				GFP_KERNEL);
> 
> How does this improve the situation? For any real life scenario this can't
> overflow, but it does add an extra (pointless) runtime check, since
> num_possible_cpus() is not a compile time constant.
> 
> So, why is this an "issue"?

It's not an issue but I for one still prefer consistent use of
kmalloc_array and kcalloc.

Paolo

WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Heiko Carstens <heiko.carstens@de.ibm.com>,
	SF Markus Elfring <elfring@users.sourceforge.net>
Cc: linux-s390@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Michael Holzheu <holzheu@linux.vnet.ibm.com>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org,
	Julia Lawall <julia.lawall@lip6.fr>
Subject: Re: [PATCH] s390/hypfs: Use kmalloc_array() in diag0c_store()
Date: Thu, 01 Sep 2016 15:39:02 +0000	[thread overview]
Message-ID: <a5ade28e-c2d3-2727-ee63-b2e285a7f316@redhat.com> (raw)
In-Reply-To: <20160901103245.GA3624@osiris>



On 01/09/2016 12:32, Heiko Carstens wrote:
> On Thu, Sep 01, 2016 at 11:38:15AM +0200, SF Markus Elfring wrote:
>> From: Markus Elfring <elfring@users.sourceforge.net>
>> Date: Thu, 1 Sep 2016 11:30:58 +0200
>>
>> A multiplication for the size determination of a memory allocation
>> indicated that an array data structure should be processed.
>> Thus use the corresponding function "kmalloc_array".
>>
>> This issue was detected by using the Coccinelle software.
>>
>> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
>> ---
>>  arch/s390/hypfs/hypfs_diag0c.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/hypfs/hypfs_diag0c.c b/arch/s390/hypfs/hypfs_diag0c.c
>> index 0f1927c..61418a8 100644
>> --- a/arch/s390/hypfs/hypfs_diag0c.c
>> +++ b/arch/s390/hypfs/hypfs_diag0c.c
>> @@ -48,7 +48,9 @@ static void *diag0c_store(unsigned int *count)
>>  
>>  	get_online_cpus();
>>  	cpu_count = num_online_cpus();
>> -	cpu_vec = kmalloc(sizeof(*cpu_vec) * num_possible_cpus(), GFP_KERNEL);
>> +	cpu_vec = kmalloc_array(num_possible_cpus(),
>> +				sizeof(*cpu_vec),
>> +				GFP_KERNEL);
> 
> How does this improve the situation? For any real life scenario this can't
> overflow, but it does add an extra (pointless) runtime check, since
> num_possible_cpus() is not a compile time constant.
> 
> So, why is this an "issue"?

It's not an issue but I for one still prefer consistent use of
kmalloc_array and kcalloc.

Paolo

  reply	other threads:[~2016-09-01 15:39 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-01  9:38 [PATCH] s390/hypfs: Use kmalloc_array() in diag0c_store() SF Markus Elfring
2016-09-01  9:38 ` SF Markus Elfring
2016-09-01 10:32 ` Heiko Carstens
2016-09-01 10:32   ` Heiko Carstens
2016-09-01 15:39   ` Paolo Bonzini [this message]
2016-09-01 15:39     ` Paolo Bonzini
2016-09-01 16:53     ` Michael Holzheu
2016-09-01 16:53       ` Michael Holzheu

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