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| author | Sean Christopherson <seanjc@google.com> | 2026-06-02 20:09:21 +0300 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2026-06-03 15:39:24 +0300 |
| commit | b408b52e7111c560dcd7d69612c2e07c59c36ae3 (patch) | |
| tree | faafee39955e7da24a8421a75ccb773d39d64b02 | |
| parent | b7a23fb0ed7e37774997f9b2029dd9dce5653d74 (diff) | |
| download | linux-b408b52e7111c560dcd7d69612c2e07c59c36ae3.tar.xz | |
KVM: selftests: Add guest_memfd regression test signed offset+size bug
Add a regression (and proof-of-bug) testcase to ensure KVM rejects an
offset+size that would result in a negative value when computed as a signed
64-bit value. KVM had a flaw where it would allow binding a memslot to a
guest_memfd instance even with a wildly out-of-range offset, if the offset
and size were both positive values, but the combined offset+size was
negative.
Use "0x7fffffffffffffffull - page_size", i.e. "INT64_MAX - page_size", for
the offset as the size of the guest_memfd file must be at least page_size
(KVM requires memslots and gmem files to be host page-size aligned). I.e.
"INT64_MAX - page_size + size" is guaranteed to generate an offset+size
that is negative when converted to a signed 64-bit value *and* honors KVM's
alignment requirements.
Reviewed-by: Ackerley Tng <ackerleytng@google.com>
Tested-by: Ackerley Tng <ackerleytng@google.com>
Link: https://patch.msgid.link/20260602170921.1304394-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | tools/testing/selftests/kvm/guest_memfd_test.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c index 4b4462c8bacd..775f99443d49 100644 --- a/tools/testing/selftests/kvm/guest_memfd_test.c +++ b/tools/testing/selftests/kvm/guest_memfd_test.c @@ -345,6 +345,16 @@ static void test_invalid_punch_hole(int fd, size_t total_size) } } +static void test_invalid_binding(struct kvm_vm *vm, int fd, size_t size) +{ + int r; + + r = __vm_set_user_memory_region2(vm, 0, KVM_MEM_GUEST_MEMFD, 0, size, 0, + fd, ALIGN_DOWN(INT64_MAX, page_size)); + TEST_ASSERT(r && errno == EINVAL, + "Memslot with out-of-range offset+size should fail"); +} + static void test_create_guest_memfd_invalid_sizes(struct kvm_vm *vm, u64 guest_memfd_flags) { @@ -456,6 +466,7 @@ static void __test_guest_memfd(struct kvm_vm *vm, u64 flags) gmem_test(file_size, vm, flags); gmem_test(fallocate, vm, flags); gmem_test(invalid_punch_hole, vm, flags); + gmem_test_vm(invalid_binding, vm, flags); } static void test_guest_memfd(unsigned long vm_type) |