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, 161 insertions, 0 deletions

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
new file mode 100644
index 000000000..308950aae
--- /dev/null
+++ b/rust/helpers/io.c
@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/io.h>
+#include <linux/ioport.h>
+
+#ifdef CONFIG_HAS_IOMEM
+__rust_helper void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
+{
+	return ioremap(offset, size);
+}
+
+__rust_helper void __iomem *rust_helper_ioremap_np(phys_addr_t offset,
+						   size_t size)
+{
+	return ioremap_np(offset, size);
+}
+
+__rust_helper void rust_helper_iounmap(void __iomem *addr)
+{
+	iounmap(addr);
+}
+#endif /* CONFIG_HAS_IOMEM */
+
+__rust_helper void rust_helper_memcpy_fromio(void *dst,
+					     const volatile void __iomem *src,
+					     size_t count)
+{
+	memcpy_fromio(dst, src, count);
+}
+
+__rust_helper void rust_helper_memcpy_toio(volatile void __iomem *dst,
+					   const void *src, size_t count)
+{
+	memcpy_toio(dst, src, count);
+}
+
+__rust_helper u8 rust_helper_readb(const void __iomem *addr)
+{
+	return readb(addr);
+}
+
+__rust_helper u16 rust_helper_readw(const void __iomem *addr)
+{
+	return readw(addr);
+}
+
+__rust_helper u32 rust_helper_readl(const void __iomem *addr)
+{
+	return readl(addr);
+}
+
+#ifdef CONFIG_64BIT
+__rust_helper u64 rust_helper_readq(const void __iomem *addr)
+{
+	return readq(addr);
+}
+#endif
+
+__rust_helper void rust_helper_writeb(u8 value, void __iomem *addr)
+{
+	writeb(value, addr);
+}
+
+__rust_helper void rust_helper_writew(u16 value, void __iomem *addr)
+{
+	writew(value, addr);
+}
+
+__rust_helper void rust_helper_writel(u32 value, void __iomem *addr)
+{
+	writel(value, addr);
+}
+
+#ifdef CONFIG_64BIT
+__rust_helper void rust_helper_writeq(u64 value, void __iomem *addr)
+{
+	writeq(value, addr);
+}
+#endif
+
+__rust_helper u8 rust_helper_readb_relaxed(const void __iomem *addr)
+{
+	return readb_relaxed(addr);
+}
+
+__rust_helper u16 rust_helper_readw_relaxed(const void __iomem *addr)
+{
+	return readw_relaxed(addr);
+}
+
+__rust_helper u32 rust_helper_readl_relaxed(const void __iomem *addr)
+{
+	return readl_relaxed(addr);
+}
+
+#ifdef CONFIG_64BIT
+__rust_helper u64 rust_helper_readq_relaxed(const void __iomem *addr)
+{
+	return readq_relaxed(addr);
+}
+#endif
+
+__rust_helper void rust_helper_writeb_relaxed(u8 value, void __iomem *addr)
+{
+	writeb_relaxed(value, addr);
+}
+
+__rust_helper void rust_helper_writew_relaxed(u16 value, void __iomem *addr)
+{
+	writew_relaxed(value, addr);
+}
+
+__rust_helper void rust_helper_writel_relaxed(u32 value, void __iomem *addr)
+{
+	writel_relaxed(value, addr);
+}
+
+#ifdef CONFIG_64BIT
+__rust_helper void rust_helper_writeq_relaxed(u64 value, void __iomem *addr)
+{
+	writeq_relaxed(value, addr);
+}
+#endif
+
+__rust_helper resource_size_t rust_helper_resource_size(struct resource *res)
+{
+	return resource_size(res);
+}
+
+__rust_helper struct resource *
+rust_helper_request_mem_region(resource_size_t start, resource_size_t n,
+			       const char *name)
+{
+	return request_mem_region(start, n, name);
+}
+
+__rust_helper void rust_helper_release_mem_region(resource_size_t start,
+						  resource_size_t n)
+{
+	release_mem_region(start, n);
+}
+
+__rust_helper struct resource *rust_helper_request_region(resource_size_t start,
+							  resource_size_t n,
+							  const char *name)
+{
+	return request_region(start, n, name);
+}
+
+__rust_helper struct resource *
+rust_helper_request_muxed_region(resource_size_t start, resource_size_t n,
+				 const char *name)
+{
+	return request_muxed_region(start, n, name);
+}
+
+__rust_helper void rust_helper_release_region(resource_size_t start,
+					      resource_size_t n)
+{
+	release_region(start, n);
+}