[PATCH v2 0/2] KVM: selftests: Fix two VMs leaked on early returns

[PATCH v2 0/2] KVM: selftests: Fix two VMs leaked on early returns

[Gokul K]

Two x86 selftests create a VM and then take an early return that skips the
kvm_vm_free() at the end of the function.  Both now jump to that existing
cleanup instead.

Patch 1 is the plain-SEV path of sev_smoke_test(), which returns straight
out of the UCALL_DONE case instead of leaving the loop.  The SEV-ES path
next to it breaks out and frees correctly.

Patch 2 is nx_huge_pages_test, which returns as soon as it has confirmed
that disabling NX huge pages is denied without CAP_SYS_BOOT.

The two patches are independent and either can be applied on its own.

Found by auditing every function under tools/testing/selftests/kvm/ that
creates a VM and later calls kvm_vm_free(), looking for returns in
between.  Seven other hits were false positives, mostly returns after
REPORT_GUEST_ASSERT() or TEST_FAIL(), which abort the process and make the
return unreachable.  Two more that do look real, in get-reg-list.c and
arm64/external_aborts.c, are left out because they belong to different
maintainers.

Compile-tested only.  This host has neither SEV (kvm_amd sev=N) nor hugetlb
configured, so both tests SKIP rather than run.

Note patch 1 touches sev_smoke_test.c, which an unrelated patch I sent
earlier also touches [1].  They modify different functions and do not
conflict in either order.

v2:
 - nx_huge_pages_test: goto the existing cleanup instead of open-coding
   kvm_vm_free() before the return, matching patch 1 (Sean)
 - Drop the claims that these paths never exercise VM teardown, and that
   the nx_huge_pages path is not obscure.  Neither justification holds
   up: teardown still happens, just at process exit, and how often a
   leaking path runs does not change whether it should be fixed (Sean)
 - Rebase onto current kvm-x86/next

[1] https://lore.kernel.org/all/20260807071026.195503-1-gokul02k@gmail.com/
v1: https://lore.kernel.org/all/20260808081050.408657-1-gokul02k@gmail.com/

Gokul K (2):
  KVM: selftests: Free the VM when the SEV smoke test's guest completes
  KVM: selftests: Free the VM when NX hugepage disabling is denied

 tools/testing/selftests/kvm/x86/nx_huge_pages_test.c | 3 ++-
 tools/testing/selftests/kvm/x86/sev_smoke_test.c     | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

-- 
2.54.0

[PATCH v2 1/2] KVM: selftests: Free the VM when the SEV smoke test's guest completes

[Gokul K]

test_sev() returns directly out of the UCALL_DONE case rather than
leaving the loop, so the plain-SEV path skips the kvm_vm_free() at the
end of the function.  The SEV-ES path is unaffected; it breaks out of
the loop and frees the VM correctly.

main() invokes test_sev() once per supported SEV VM type, so a full run
leaks a VM and its file descriptors.  Nothing fails today because the
process exits shortly afterwards, which is presumably why this was not
noticed, but the leak also means the plain-SEV path never exercises VM
teardown.

Use a goto so UCALL_DONE joins the existing exit path.  A plain break
would only leave the switch statement and spin the loop again.

Fixes: be250ff437fa ("KVM: selftests: Add a basic SEV smoke test")
Signed-off-by: Gokul K <gokul02k@gmail.com>
---
 tools/testing/selftests/kvm/x86/sev_smoke_test.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86/sev_smoke_test.c b/tools/testing/selftests/kvm/x86/sev_smoke_test.c
index 6b2cbe2a90b7..646ae93e3c46 100644
--- a/tools/testing/selftests/kvm/x86/sev_smoke_test.c
+++ b/tools/testing/selftests/kvm/x86/sev_smoke_test.c
@@ -178,7 +178,7 @@ static void test_sev(void *guest_code, u32 type, u64 policy)
 		case UCALL_SYNC:
 			continue;
 		case UCALL_DONE:
-			return;
+			goto done;
 		case UCALL_ABORT:
 			REPORT_GUEST_ASSERT(uc);
 		default:
@@ -187,6 +187,7 @@ static void test_sev(void *guest_code, u32 type, u64 policy)
 		}
 	}
 
+done:
 	kvm_vm_free(vm);
 }
 
-- 
2.54.0

[PATCH v2 2/2] KVM: selftests: Free the VM when NX hugepage disabling is denied

[Gokul K]

run_test() returns as soon as it has confirmed that disabling NX huge
pages fails with -EPERM, without freeing the VM created a few lines
earlier.

Jump to the kvm_vm_free() at the end of the function instead, matching
the pattern used for the SEV smoke test in the previous patch.

Fixes: b774da3f2e57 ("KVM: selftests: Test disabling NX hugepages on a VM")
Signed-off-by: Gokul K <gokul02k@gmail.com>
---
 tools/testing/selftests/kvm/x86/nx_huge_pages_test.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86/nx_huge_pages_test.c b/tools/testing/selftests/kvm/x86/nx_huge_pages_test.c
index 70950067b989..e3b20033a884 100644
--- a/tools/testing/selftests/kvm/x86/nx_huge_pages_test.c
+++ b/tools/testing/selftests/kvm/x86/nx_huge_pages_test.c
@@ -120,7 +120,7 @@ void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,
 		} else {
 			TEST_ASSERT(r == -1 && errno == EPERM,
 				    "This process should not have permission to disable NX huge pages");
-			return;
+			goto done;
 		}
 	}
 
@@ -213,6 +213,7 @@ void run_test(int reclaim_period_ms, bool disable_nx_huge_pages,
 	check_2m_page_count(vm, disable_nx_huge_pages ? 3 : 2);
 	check_split_count(vm, 0);
 
+done:
 	kvm_vm_free(vm);
 }
 
-- 
2.54.0

Re: [PATCH v2 0/2] KVM: selftests: Fix two VMs leaked on early returns

[Sean Christopherson]

On Tue, 11 Aug 2026 10:30:27 +0530, Gokul K wrote:
> Two x86 selftests create a VM and then take an early return that skips the
> kvm_vm_free() at the end of the function.  Both now jump to that existing
> cleanup instead.
> 
> Patch 1 is the plain-SEV path of sev_smoke_test(), which returns straight
> out of the UCALL_DONE case instead of leaving the loop.  The SEV-ES path
> next to it breaks out and frees correctly.
> 
> [...]

Applied to kvm-x86 selftests, thanks!

[1/2] KVM: selftests: Free the VM when the SEV smoke test's guest completes
      https://github.com/kvm-x86/linux/commit/434c50e703c5
[2/2] KVM: selftests: Free the VM when NX hugepage disabling is denied
      https://github.com/kvm-x86/linux/commit/ebb702707896

--
https://github.com/kvm-x86/linux/tree/next