Re: [PATCH] KVM: selftests: Add 'malloc' failure check in test_vmx_nested_state

Andrew Jones
2024-04-23T15:14:55Z

On Tue, Apr 23, 2024 at 07:56:01AM -0700, Sean Christopherson wrote:
> +others
>
> On Tue, Apr 23, 2024, Markus Elfring wrote:
> > …
> > > This patch will add the malloc failure checking
> > …
> >
> > * Please use a corresponding imperative wording for the change description.
> >
> > * Would you like to add the tag “Fixes” accordingly?
>
> Nah, don't bother with Fixes. OOM will cause the test to fail regardless, the
> fact that it gets an assert instead a NULL pointer deref is nice to have, but by
> no means does it fix a bug.
>
> > > +++ b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
> > > @@ -91,6 +91,7 @@ void test_vmx_nested_state(struct kvm_vcpu *vcpu)
> > > const int state_sz = sizeof(struct kvm_nested_state) + getpagesize();
> > > struct kvm_nested_state *state =
> > > (struct kvm_nested_state *)malloc(state_sz);
> > > + TEST_ASSERT(state, "-ENOMEM when allocating kvm state");
> > …
> >
> > Can “errno” be relevant for the error message construction?
>
> Probably not, but there's also no reason to assume ENOMEM. TEST_ASSERT() spits
> out the actual errno, and we can just say something like "malloc() failed for
> blah blah blah".
>
> But rather than keeping playing whack-a-mole, what if we add macros to perform
> allocations and assert on the result? I have zero interest in chasing down all
> of the "unsafe" allocations, and odds are very good that we'll collectively fail
> to enforce checking on new code.
>
> E.g. something like (obviously won't compile, just for demonstration purposes)
>
> #define kvm_malloc(x)
> ({
> void *__ret;
>
> __ret = malloc(x);
> TEST_ASSERT(__ret, "Failed malloc(" #x ")\n");
> __ret;
> })
>
> #define kvm_calloc(x, y)
> ({
> void *__ret;
>
> __ret = calloc(x, y);
> TEST_ASSERT(__ret, "Failed calloc(" #x ", " #y ")\n");
> __ret;
> })

Sounds good to me, but I'd call them test_malloc, test_calloc, etc. and
put them in include/test_util.h

Thanks,
drew