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/drivers/iommu/iommu-debugfs.c b/drivers/iommu/iommu-debugfs.c
new file mode 100644
index 000000000..f03548942
--- /dev/null
+++ b/drivers/iommu/iommu-debugfs.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * IOMMU debugfs core infrastructure
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Gary R Hook <gary.hook@amd.com>
+ */
+
+#include <linux/pci.h>
+#include <linux/iommu.h>
+#include <linux/debugfs.h>
+
+struct dentry *iommu_debugfs_dir;
+EXPORT_SYMBOL_GPL(iommu_debugfs_dir);
+
+/**
+ * iommu_debugfs_setup - create the top-level iommu directory in debugfs
+ *
+ * Provide base enablement for using debugfs to expose internal data of an
+ * IOMMU driver. When called, this function creates the
+ * /sys/kernel/debug/iommu directory.
+ *
+ * Emit a strong warning at boot time to indicate that this feature is
+ * enabled.
+ *
+ * This function is called from iommu_init; drivers may then use
+ * iommu_debugfs_dir to instantiate a vendor-specific directory to be used
+ * to expose internal data.
+ */
+void iommu_debugfs_setup(void)
+{
+	if (!iommu_debugfs_dir) {
+		iommu_debugfs_dir = debugfs_create_dir("iommu", NULL);
+		pr_warn("\n");
+		pr_warn("*************************************************************\n");
+		pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE    **\n");
+		pr_warn("**                                                         **\n");
+		pr_warn("**  IOMMU DebugFS SUPPORT HAS BEEN ENABLED IN THIS KERNEL  **\n");
+		pr_warn("**                                                         **\n");
+		pr_warn("** This means that this kernel is built to expose internal **\n");
+		pr_warn("** IOMMU data structures, which may compromise security on **\n");
+		pr_warn("** your system.                                            **\n");
+		pr_warn("**                                                         **\n");
+		pr_warn("** If you see this message and you are not debugging the   **\n");
+		pr_warn("** kernel, report this immediately to your vendor!         **\n");
+		pr_warn("**                                                         **\n");
+		pr_warn("**     NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE    **\n");
+		pr_warn("*************************************************************\n");
+	}
+}