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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 <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
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