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, 63 insertions, 0 deletions

diff --git a/arch/x86/mm/pgprot.c b/arch/x86/mm/pgprot.c
new file mode 100644
index 000000000..dc1afd5c8
--- /dev/null
+++ b/arch/x86/mm/pgprot.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <asm/pgtable.h>
+#include <asm/mem_encrypt.h>
+
+static pgprot_t protection_map[16] __ro_after_init = {
+	[VM_NONE]					= PAGE_NONE,
+	[VM_READ]					= PAGE_READONLY,
+	[VM_WRITE]					= PAGE_COPY,
+	[VM_WRITE | VM_READ]				= PAGE_COPY,
+	[VM_EXEC]					= PAGE_READONLY_EXEC,
+	[VM_EXEC | VM_READ]				= PAGE_READONLY_EXEC,
+	[VM_EXEC | VM_WRITE]				= PAGE_COPY_EXEC,
+	[VM_EXEC | VM_WRITE | VM_READ]			= PAGE_COPY_EXEC,
+	[VM_SHARED]					= PAGE_NONE,
+	[VM_SHARED | VM_READ]				= PAGE_READONLY,
+	[VM_SHARED | VM_WRITE]				= PAGE_SHARED,
+	[VM_SHARED | VM_WRITE | VM_READ]		= PAGE_SHARED,
+	[VM_SHARED | VM_EXEC]				= PAGE_READONLY_EXEC,
+	[VM_SHARED | VM_EXEC | VM_READ]			= PAGE_READONLY_EXEC,
+	[VM_SHARED | VM_EXEC | VM_WRITE]		= PAGE_SHARED_EXEC,
+	[VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]	= PAGE_SHARED_EXEC
+};
+
+void add_encrypt_protection_map(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(protection_map); i++)
+		protection_map[i] = pgprot_encrypted(protection_map[i]);
+}
+
+pgprot_t vm_get_page_prot(vm_flags_t vm_flags)
+{
+	unsigned long val = pgprot_val(protection_map[vm_flags &
+				      (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]);
+
+#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
+	/*
+	 * Take the 4 protection key bits out of the vma->vm_flags value and
+	 * turn them in to the bits that we can put in to a pte.
+	 *
+	 * Only override these if Protection Keys are available (which is only
+	 * on 64-bit).
+	 */
+	if (vm_flags & VM_PKEY_BIT0)
+		val |= _PAGE_PKEY_BIT0;
+	if (vm_flags & VM_PKEY_BIT1)
+		val |= _PAGE_PKEY_BIT1;
+	if (vm_flags & VM_PKEY_BIT2)
+		val |= _PAGE_PKEY_BIT2;
+	if (vm_flags & VM_PKEY_BIT3)
+		val |= _PAGE_PKEY_BIT3;
+#endif
+
+	val = __sme_set(val);
+	if (val & _PAGE_PRESENT)
+		val &= __supported_pte_mask;
+	return __pgprot(val);
+}
+EXPORT_SYMBOL(vm_get_page_prot);