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, 36 insertions, 0 deletions

diff --git a/arch/alpha/math-emu/sfp-util.h b/arch/alpha/math-emu/sfp-util.h
new file mode 100644
index 000000000..ae30f3417
--- /dev/null
+++ b/arch/alpha/math-emu/sfp-util.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <asm/byteorder.h>
+#include <asm/fpu.h>
+
+#define add_ssaaaa(sh, sl, ah, al, bh, bl) \
+  ((sl) = (al) + (bl), (sh) = (ah) + (bh) + ((sl) < (al)))
+
+#define sub_ddmmss(sh, sl, ah, al, bh, bl) \
+  ((sl) = (al) - (bl), (sh) = (ah) - (bh) - ((al) < (bl)))
+
+#define umul_ppmm(wh, wl, u, v)			\
+  __asm__ ("mulq %2,%3,%1; umulh %2,%3,%0"	\
+	   : "=r" ((UDItype)(wh)),		\
+	     "=&r" ((UDItype)(wl))		\
+	   : "r" ((UDItype)(u)),		\
+	     "r" ((UDItype)(v)))
+
+#define udiv_qrnnd(q, r, n1, n0, d)				\
+  do { unsigned long __r;					\
+    (q) = __udiv_qrnnd (&__r, (n1), (n0), (d));			\
+    (r) = __r;							\
+  } while (0)
+extern unsigned long __udiv_qrnnd (unsigned long *, unsigned long,
+				   unsigned long , unsigned long);
+
+#define UDIV_NEEDS_NORMALIZATION 1  
+
+#define abort()			goto bad_insn
+
+#ifndef __LITTLE_ENDIAN
+#define __LITTLE_ENDIAN -1
+#endif
+#define __BYTE_ORDER __LITTLE_ENDIAN