Re: [PATCH v8 43/46] KVM: selftests: Check fd/flags provided to mmap() when setting up memslot
From: Fuad Tabba <hidden>
Date: 2026-06-25 09:20:20
Also in:
kvm, linux-coco, linux-doc, linux-kselftest, linux-mm, lkml
On Fri, 19 Jun 2026 at 01:32, Ackerley Tng via B4 Relay [off-list ref] wrote:
From: Sean Christopherson <seanjc@google.com> Check that a valid fd provided to mmap() must be accompanied by MAP_SHARED. With an invalid fd (usually used for anonymous mappings), there are no constraints on mmap() flags. Add this check to make sure that when a guest_memfd is used as region->fd, the flag provided to mmap() will include MAP_SHARED. Signed-off-by: Sean Christopherson <seanjc@google.com> [Rephrase assertion message.] Signed-off-by: Ackerley Tng <redacted>
Reviewed-by: Fuad Tabba <redacted> Cheers, /fuad
quoted hunk ↗ jump to hunk
--- tools/testing/selftests/kvm/lib/kvm_util.c | 3 +++ 1 file changed, 3 insertions(+)diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c index 0b2256ea65ff9..6b304e8a0e0d5 100644 --- a/tools/testing/selftests/kvm/lib/kvm_util.c +++ b/tools/testing/selftests/kvm/lib/kvm_util.c@@ -1110,6 +1110,9 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type, src_type == VM_MEM_SRC_SHARED_HUGETLB); } + TEST_ASSERT(region->fd == -1 || backing_src_is_shared(src_type), + "A valid fd provided to mmap() must be accompanied by MAP_SHARED."); + region->mmap_start = __kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE, vm_mem_backing_src_alias(src_type)->flag, region->fd, mmap_offset); --2.55.0.rc0.738.g0c8ab3ebcc-goog