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, 70 insertions, 0 deletions

diff --git a/include/asm-generic/bitops/atomic.h b/include/asm-generic/bitops/atomic.h
new file mode 100644
index 000000000..e076e079f
--- /dev/null
+++ b/include/asm-generic/bitops/atomic.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_GENERIC_BITOPS_ATOMIC_H_
+#define _ASM_GENERIC_BITOPS_ATOMIC_H_
+
+#include <linux/atomic.h>
+#include <linux/compiler.h>
+#include <asm/barrier.h>
+
+/*
+ * Implementation of atomic bitops using atomic-fetch ops.
+ * See Documentation/atomic_bitops.txt for details.
+ */
+
+static __always_inline void
+arch_set_bit(unsigned int nr, volatile unsigned long *p)
+{
+	p += BIT_WORD(nr);
+	raw_atomic_long_or(BIT_MASK(nr), (atomic_long_t *)p);
+}
+
+static __always_inline void
+arch_clear_bit(unsigned int nr, volatile unsigned long *p)
+{
+	p += BIT_WORD(nr);
+	raw_atomic_long_andnot(BIT_MASK(nr), (atomic_long_t *)p);
+}
+
+static __always_inline void
+arch_change_bit(unsigned int nr, volatile unsigned long *p)
+{
+	p += BIT_WORD(nr);
+	raw_atomic_long_xor(BIT_MASK(nr), (atomic_long_t *)p);
+}
+
+static __always_inline int
+arch_test_and_set_bit(unsigned int nr, volatile unsigned long *p)
+{
+	long old;
+	unsigned long mask = BIT_MASK(nr);
+
+	p += BIT_WORD(nr);
+	old = raw_atomic_long_fetch_or(mask, (atomic_long_t *)p);
+	return !!(old & mask);
+}
+
+static __always_inline int
+arch_test_and_clear_bit(unsigned int nr, volatile unsigned long *p)
+{
+	long old;
+	unsigned long mask = BIT_MASK(nr);
+
+	p += BIT_WORD(nr);
+	old = raw_atomic_long_fetch_andnot(mask, (atomic_long_t *)p);
+	return !!(old & mask);
+}
+
+static __always_inline int
+arch_test_and_change_bit(unsigned int nr, volatile unsigned long *p)
+{
+	long old;
+	unsigned long mask = BIT_MASK(nr);
+
+	p += BIT_WORD(nr);
+	old = raw_atomic_long_fetch_xor(mask, (atomic_long_t *)p);
+	return !!(old & mask);
+}
+
+#include <asm-generic/bitops/instrumented-atomic.h>
+
+#endif /* _ASM_GENERIC_BITOPS_ATOMIC_H */