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SubjectRe: [PATCH] kvm: Use struct_size() in kmalloc()
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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;
>>

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