From: Sean Christopherson Date: Thu, 17 Aug 2023 23:34:30 +0000 (-0700) Subject: KVM: selftests: Explicit set #UD when *potentially* injecting exception X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=02dc2543e3795867260826983bf3f20b282c8fc3;p=linux.git KVM: selftests: Explicit set #UD when *potentially* injecting exception Explicitly set the exception vector to #UD when potentially injecting an exception in sync_regs_test's subtests that try to detect TOCTOU bugs in KVM's handling of exceptions injected by userspace. A side effect of the original KVM bug was that KVM would clear the vector, but relying on KVM to clear the vector (i.e. make it #DE) makes it less likely that the test would ever find *new* KVM bugs, e.g. because only the first iteration would run with a legal vector to start. Explicitly inject #UD for race_events_inj_pen() as well, e.g. so that it doesn't inherit the illegal 255 vector from race_events_exc(), which currently runs first. Link: https://lore.kernel.org/r/20230817233430.1416463-3-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c index 21e99dae2ff2c..00965ba33f730 100644 --- a/tools/testing/selftests/kvm/x86_64/sync_regs_test.c +++ b/tools/testing/selftests/kvm/x86_64/sync_regs_test.c @@ -91,6 +91,8 @@ static void *race_events_inj_pen(void *arg) struct kvm_run *run = (struct kvm_run *)arg; struct kvm_vcpu_events *events = &run->s.regs.events; + WRITE_ONCE(events->exception.nr, UD_VECTOR); + for (;;) { WRITE_ONCE(run->kvm_dirty_regs, KVM_SYNC_X86_EVENTS); WRITE_ONCE(events->flags, 0); @@ -115,6 +117,7 @@ static void *race_events_exc(void *arg) for (;;) { WRITE_ONCE(run->kvm_dirty_regs, KVM_SYNC_X86_EVENTS); WRITE_ONCE(events->flags, 0); + WRITE_ONCE(events->exception.nr, UD_VECTOR); WRITE_ONCE(events->exception.pending, 1); WRITE_ONCE(events->exception.nr, 255);