[PATCH] kvm: Use struct_size() in kmalloc()

[PATCH] kvm: Use struct_size() in kmalloc()

[Gustavo A. R. Silva]

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    void *entry[];
};

instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 virt/kvm/kvm_main.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 666d0155662d..635b12fdbab8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3709,8 +3709,8 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
 	if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
 		return -ENOSPC;
 
-	new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count + 1) *
-			  sizeof(struct kvm_io_range)), GFP_KERNEL);
+	new_bus = kmalloc(struct_size(bus, range, bus->dev_count + 1),
+			  GFP_KERNEL);
 	if (!new_bus)
 		return -ENOMEM;
 
@@ -3755,8 +3755,8 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
 	if (i == bus->dev_count)
 		return;
 
-	new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count - 1) *
-			  sizeof(struct kvm_io_range)), GFP_KERNEL);
+	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
+			  GFP_KERNEL);
 	if (!new_bus)  {
 		pr_err("kvm: failed to shrink bus, removing it completely\n");
 		goto broken;
-- 
2.20.1

Re: [PATCH] kvm: Use struct_size() in kmalloc()

[Radim Krčmář]

2019-01-04 10:29-0600, Gustavo A. R. Silva:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct foo {
>     int stuff;
>     void *entry[];
> };
> 
> instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---

Queued, thanks.

Re: [PATCH] kvm: Use struct_size() in kmalloc()

[Gustavo A. R. Silva]

Hi all,

Friendly ping:

Who can take this?

Thanks
--
Gustavo

On 1/4/19 10:29 AM, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct foo {
>     int stuff;
>     void *entry[];
> };
> 
> instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  virt/kvm/kvm_main.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 666d0155662d..635b12fdbab8 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3709,8 +3709,8 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>  	if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
>  		return -ENOSPC;
>  
> -	new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count + 1) *
> -			  sizeof(struct kvm_io_range)), GFP_KERNEL);
> +	new_bus = kmalloc(struct_size(bus, range, bus->dev_count + 1),
> +			  GFP_KERNEL);
>  	if (!new_bus)
>  		return -ENOMEM;
>  
> @@ -3755,8 +3755,8 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>  	if (i == bus->dev_count)
>  		return;
>  
> -	new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count - 1) *
> -			  sizeof(struct kvm_io_range)), GFP_KERNEL);
> +	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
> +			  GFP_KERNEL);
>  	if (!new_bus)  {
>  		pr_err("kvm: failed to shrink bus, removing it completely\n");
>  		goto broken;
> 

Re: [PATCH] kvm: Use struct_size() in kmalloc()

[Paolo Bonzini]

On 29/01/19 18:20, Gustavo A. R. Silva wrote:
> Hi all,
> 
> Friendly ping:
> 
> Who can take this?

I cannot find the original message in my inbox, but I've queued it from
the quote below.

Thanks,

Paolo

> Thanks
> --
> Gustavo
> 
> On 1/4/19 10:29 AM, Gustavo A. R. Silva wrote:
>> One of the more common cases of allocation size calculations is finding
>> the size of a structure that has a zero-sized array at the end, along
>> with memory for some number of elements for that array. For example:
>>
>> struct foo {
>>     int stuff;
>>     void *entry[];
>> };
>>
>> instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
>>
>> Instead of leaving these open-coded and prone to type mistakes, we can
>> now use the new struct_size() helper:
>>
>> instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
>>
>> This code was detected with the help of Coccinelle.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>> ---
>>  virt/kvm/kvm_main.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>> index 666d0155662d..635b12fdbab8 100644
>> --- a/virt/kvm/kvm_main.c
>> +++ b/virt/kvm/kvm_main.c
>> @@ -3709,8 +3709,8 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
>>  	if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
>>  		return -ENOSPC;
>>  
>> -	new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count + 1) *
>> -			  sizeof(struct kvm_io_range)), GFP_KERNEL);
>> +	new_bus = kmalloc(struct_size(bus, range, bus->dev_count + 1),
>> +			  GFP_KERNEL);
>>  	if (!new_bus)
>>  		return -ENOMEM;
>>  
>> @@ -3755,8 +3755,8 @@ void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
>>  	if (i == bus->dev_count)
>>  		return;
>>  
>> -	new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count - 1) *
>> -			  sizeof(struct kvm_io_range)), GFP_KERNEL);
>> +	new_bus = kmalloc(struct_size(bus, range, bus->dev_count - 1),
>> +			  GFP_KERNEL);
>>  	if (!new_bus)  {
>>  		pr_err("kvm: failed to shrink bus, removing it completely\n");
>>  		goto broken;
>>

Re: [PATCH] kvm: Use struct_size() in kmalloc()

[Gustavo A. R. Silva]

On 1/30/19 10:08 AM, Paolo Bonzini wrote:
> On 29/01/19 18:20, Gustavo A. R. Silva wrote:
>> Hi all,
>>
>> Friendly ping:
>>
>> Who can take this?
> 
> I cannot find the original message in my inbox, but I've queued it from
> the quote below.
> 

Thank you, Paolo.

--
Gustavo