selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/rust/helpers/drm_gpuvm.c b/rust/helpers/drm_gpuvm.c
new file mode 100644
index 000000000..4130b6325
--- /dev/null
+++ b/rust/helpers/drm_gpuvm.c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+
+#ifdef CONFIG_RUST_DRM_GPUVM
+
+#include <drm/drm_gpuvm.h>
+
+__rust_helper
+struct drm_gpuvm_bo *rust_helper_drm_gpuvm_bo_get(struct drm_gpuvm_bo *vm_bo)
+{
+	return drm_gpuvm_bo_get(vm_bo);
+}
+
+__rust_helper
+struct drm_gpuvm *rust_helper_drm_gpuvm_get(struct drm_gpuvm *obj)
+{
+	return drm_gpuvm_get(obj);
+}
+
+__rust_helper
+bool rust_helper_drm_gpuvm_is_extobj(struct drm_gpuvm *gpuvm,
+				     struct drm_gem_object *obj)
+{
+	return drm_gpuvm_is_extobj(gpuvm, obj);
+}
+
+#endif // CONFIG_RUST_DRM_GPUVM