Commit a585b876 authored by James Houghton's avatar James Houghton Committed by Sean Christopherson
Browse files

KVM: selftests: Fix signedness issue with vCPU mmap size check 



Check that the return value of KVM_GET_VCPU_MMAP_SIZE is non-negative
before comparing with sizeof(kvm_run). If KVM_GET_VCPU_MMAP_SIZE fails,
it will return -1, and `-1 > sizeof(kvm_run)` is true, so the ASSERT
passes.

There are no other locations in tools/testing/selftests/kvm that make
the same mistake.

Signed-off-by: default avatarJames Houghton <jthoughton@google.com>
Link: https://lore.kernel.org/r/20250711001742.1965347-1-jthoughton@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent c17b750b

tools/testing/selftests/kvm/lib/kvm_util.c

+4 −4
Original line number Diff line number Diff line
@@ -24,7 +24,7 @@ uint32_t guest_random_seed; 
struct guest_random_state guest_rng;

static uint32_t last_guest_seed;



static int vcpu_mmap_sz(void);

static size_t vcpu_mmap_sz(void);



int __open_path_or_exit(const char *path, int flags, const char *enoent_help)

{
@@ -1321,14 +1321,14 @@ void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t base, uint64_t size, 
}



/* Returns the size of a vCPU's kvm_run structure. */

static int vcpu_mmap_sz(void)

static size_t vcpu_mmap_sz(void)

{

	int dev_fd, ret;



	dev_fd = open_kvm_dev_path_or_exit();



	ret = ioctl(dev_fd, KVM_GET_VCPU_MMAP_SIZE, NULL);

	TEST_ASSERT(ret >= sizeof(struct kvm_run),

	TEST_ASSERT(ret >= 0 && ret >= sizeof(struct kvm_run),

		    KVM_IOCTL_ERROR(KVM_GET_VCPU_MMAP_SIZE, ret));



	close(dev_fd);
@@ -1369,7 +1369,7 @@ struct kvm_vcpu *__vm_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id) 
	TEST_ASSERT_VM_VCPU_IOCTL(vcpu->fd >= 0, KVM_CREATE_VCPU, vcpu->fd, vm);



	TEST_ASSERT(vcpu_mmap_sz() >= sizeof(*vcpu->run), "vcpu mmap size "

		"smaller than expected, vcpu_mmap_sz: %i expected_min: %zi",

		"smaller than expected, vcpu_mmap_sz: %zi expected_min: %zi",

		vcpu_mmap_sz(), sizeof(*vcpu->run));

	vcpu->run = (struct kvm_run *) mmap(NULL, vcpu_mmap_sz(),

		PROT_READ | PROT_WRITE, MAP_SHARED, vcpu->fd, 0);