[PATCH] KVM: irqchip: Use struct_size() in kzalloc()

[PATCH] KVM: irqchip: Use struct_size() in kzalloc()

[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;
   struct boo entry[];
};

instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), GFP_KERNEL);

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

instance = kzalloc(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/irqchip.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
index 79e59e4fa3dc..f8be6a3d1aa6 100644
--- a/virt/kvm/irqchip.c
+++ b/virt/kvm/irqchip.c
@@ -196,9 +196,7 @@ int kvm_set_irq_routing(struct kvm *kvm,
 
 	nr_rt_entries += 1;
 
-	new = kzalloc(sizeof(*new) + (nr_rt_entries * sizeof(struct hlist_head)),
-		      GFP_KERNEL_ACCOUNT);
-
+	new = kzalloc(struct_size(new, map, nr_rt_entries), GFP_KERNEL_ACCOUNT);
 	if (!new)
 		return -ENOMEM;
 
-- 
2.21.0

Re: [PATCH] KVM: irqchip: Use struct_size() in kzalloc()

[Paolo Bonzini]

On 31/05/19 21:24, 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;
>    struct boo entry[];
> };
> 
> instance = kzalloc(sizeof(struct foo) + count * sizeof(struct boo), GFP_KERNEL);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> instance = kzalloc(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/irqchip.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
> index 79e59e4fa3dc..f8be6a3d1aa6 100644
> --- a/virt/kvm/irqchip.c
> +++ b/virt/kvm/irqchip.c
> @@ -196,9 +196,7 @@ int kvm_set_irq_routing(struct kvm *kvm,
>  
>  	nr_rt_entries += 1;
>  
> -	new = kzalloc(sizeof(*new) + (nr_rt_entries * sizeof(struct hlist_head)),
> -		      GFP_KERNEL_ACCOUNT);
> -
> +	new = kzalloc(struct_size(new, map, nr_rt_entries), GFP_KERNEL_ACCOUNT);
>  	if (!new)
>  		return -ENOMEM;
>  
> 

Queued, thanks.

Paolo

Re: [PATCH] KVM: irqchip: Use struct_size() in kzalloc()

[Gustavo A. R. Silva]

On 6/4/19 12:20 PM, Paolo Bonzini wrote:
> 
> Queued, thanks.
> 

Great. :)

Thanks, Paolo.
--
Gustavo