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, 48 insertions, 0 deletions

diff --git a/arch/powerpc/math-emu/fcmpo.c b/arch/powerpc/math-emu/fcmpo.c
new file mode 100644
index 000000000..f437d0896
--- /dev/null
+++ b/arch/powerpc/math-emu/fcmpo.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/uaccess.h>
+
+#include <asm/sfp-machine.h>
+#include <math-emu/soft-fp.h>
+#include <math-emu/double.h>
+
+int
+fcmpo(u32 *ccr, int crfD, void *frA, void *frB)
+{
+	FP_DECL_D(A);
+	FP_DECL_D(B);
+	FP_DECL_EX;
+	int code[4] = { (1 << 3), (1 << 1), (1 << 2), (1 << 0) };
+	long cmp;
+
+#ifdef DEBUG
+	printk("%s: %p (%08x) %d %p %p\n", __func__, ccr, *ccr, crfD, frA, frB);
+#endif
+
+	FP_UNPACK_DP(A, frA);
+	FP_UNPACK_DP(B, frB);
+
+#ifdef DEBUG
+	printk("A: %ld %lu %lu %ld (%ld)\n", A_s, A_f1, A_f0, A_e, A_c);
+	printk("B: %ld %lu %lu %ld (%ld)\n", B_s, B_f1, B_f0, B_e, B_c);
+#endif
+
+	if (A_c == FP_CLS_NAN || B_c == FP_CLS_NAN)
+		FP_SET_EXCEPTION(EFLAG_VXVC);
+
+	FP_CMP_D(cmp, A, B, 2);
+	cmp = code[(cmp + 1) & 3];
+
+	__FPU_FPSCR &= ~(0x1f000);
+	__FPU_FPSCR |= (cmp << 12);
+
+	*ccr &= ~(15 << ((7 - crfD) << 2));
+	*ccr |= (cmp << ((7 - crfD) << 2));
+
+#ifdef DEBUG
+	printk("CR: %08x\n", *ccr);
+#endif
+
+	return FP_CUR_EXCEPTIONS;
+}