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, 51 insertions, 0 deletions

diff --git a/rust/helpers/dma.c b/rust/helpers/dma.c
new file mode 100644
index 000000000..9fbeb507b
--- /dev/null
+++ b/rust/helpers/dma.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-mapping.h>
+
+__rust_helper void *rust_helper_dma_alloc_attrs(struct device *dev, size_t size,
+						dma_addr_t *dma_handle,
+						gfp_t flag, unsigned long attrs)
+{
+	return dma_alloc_attrs(dev, size, dma_handle, flag, attrs);
+}
+
+__rust_helper void rust_helper_dma_free_attrs(struct device *dev, size_t size,
+					      void *cpu_addr,
+					      dma_addr_t dma_handle,
+					      unsigned long attrs)
+{
+	dma_free_attrs(dev, size, cpu_addr, dma_handle, attrs);
+}
+
+__rust_helper int rust_helper_dma_set_mask_and_coherent(struct device *dev,
+							u64 mask)
+{
+	return dma_set_mask_and_coherent(dev, mask);
+}
+
+__rust_helper int rust_helper_dma_set_mask(struct device *dev, u64 mask)
+{
+	return dma_set_mask(dev, mask);
+}
+
+__rust_helper int rust_helper_dma_set_coherent_mask(struct device *dev, u64 mask)
+{
+	return dma_set_coherent_mask(dev, mask);
+}
+
+__rust_helper int rust_helper_dma_map_sgtable(struct device *dev, struct sg_table *sgt,
+					      enum dma_data_direction dir, unsigned long attrs)
+{
+	return dma_map_sgtable(dev, sgt, dir, attrs);
+}
+
+__rust_helper size_t rust_helper_dma_max_mapping_size(struct device *dev)
+{
+	return dma_max_mapping_size(dev);
+}
+
+__rust_helper void rust_helper_dma_set_max_seg_size(struct device *dev,
+						    unsigned int size)
+{
+	dma_set_max_seg_size(dev, size);
+}