2019-01-04 17:44:21

by Gustavo A. R. Silva

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

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 <[email protected]>
---
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

2019-01-11 14:22:56

by Radim Krčmář

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

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 <[email protected]>
> ---

Queued, thanks.

2019-01-29 17:37:18

by Gustavo A. R. Silva

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

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 <[email protected]>
> ---
> 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;
>

2019-01-30 16:10:51

by Paolo Bonzini

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

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 <[email protected]>
>> ---
>> 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;
>>

2019-01-30 16:14:51

by Gustavo A. R. Silva

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

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