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, 99 insertions, 0 deletions

diff --git a/arch/mips/math-emu/ieee754d.c b/arch/mips/math-emu/ieee754d.c
new file mode 100644
index 000000000..586c4db2d
--- /dev/null
+++ b/arch/mips/math-emu/ieee754d.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Some debug functions
+ *
+ * MIPS floating point support
+ *
+ * Copyright (C) 1994-2000 Algorithmics Ltd.
+ *
+ *  Nov 7, 2000
+ *  Modified to build and operate in Linux kernel environment.
+ *
+ *  Kevin D. Kissell, kevink@mips.com and Carsten Langgaard, carstenl@mips.com
+ *  Copyright (C) 2000 MIPS Technologies, Inc. All rights reserved.
+ */
+
+#include <linux/types.h>
+#include <linux/printk.h>
+#include "ieee754.h"
+#include "ieee754sp.h"
+#include "ieee754dp.h"
+
+union ieee754dp ieee754dp_dump(char *m, union ieee754dp x)
+{
+	int i;
+
+	printk("%s", m);
+	printk("<%08x,%08x>\n", (unsigned) (x.bits >> 32),
+	       (unsigned) x.bits);
+	printk("\t=");
+	switch (ieee754dp_class(x)) {
+	case IEEE754_CLASS_QNAN:
+	case IEEE754_CLASS_SNAN:
+		printk("Nan %c", DPSIGN(x) ? '-' : '+');
+		for (i = DP_FBITS - 1; i >= 0; i--)
+			printk("%c", DPMANT(x) & DP_MBIT(i) ? '1' : '0');
+		break;
+	case IEEE754_CLASS_INF:
+		printk("%cInfinity", DPSIGN(x) ? '-' : '+');
+		break;
+	case IEEE754_CLASS_ZERO:
+		printk("%cZero", DPSIGN(x) ? '-' : '+');
+		break;
+	case IEEE754_CLASS_DNORM:
+		printk("%c0.", DPSIGN(x) ? '-' : '+');
+		for (i = DP_FBITS - 1; i >= 0; i--)
+			printk("%c", DPMANT(x) & DP_MBIT(i) ? '1' : '0');
+		printk("e%d", DPBEXP(x) - DP_EBIAS);
+		break;
+	case IEEE754_CLASS_NORM:
+		printk("%c1.", DPSIGN(x) ? '-' : '+');
+		for (i = DP_FBITS - 1; i >= 0; i--)
+			printk("%c", DPMANT(x) & DP_MBIT(i) ? '1' : '0');
+		printk("e%d", DPBEXP(x) - DP_EBIAS);
+		break;
+	default:
+		printk("Illegal/Unknown IEEE754 value class");
+	}
+	printk("\n");
+	return x;
+}
+
+union ieee754sp ieee754sp_dump(char *m, union ieee754sp x)
+{
+	int i;
+
+	printk("%s=", m);
+	printk("<%08x>\n", (unsigned) x.bits);
+	printk("\t=");
+	switch (ieee754sp_class(x)) {
+	case IEEE754_CLASS_QNAN:
+	case IEEE754_CLASS_SNAN:
+		printk("Nan %c", SPSIGN(x) ? '-' : '+');
+		for (i = SP_FBITS - 1; i >= 0; i--)
+			printk("%c", SPMANT(x) & SP_MBIT(i) ? '1' : '0');
+		break;
+	case IEEE754_CLASS_INF:
+		printk("%cInfinity", SPSIGN(x) ? '-' : '+');
+		break;
+	case IEEE754_CLASS_ZERO:
+		printk("%cZero", SPSIGN(x) ? '-' : '+');
+		break;
+	case IEEE754_CLASS_DNORM:
+		printk("%c0.", SPSIGN(x) ? '-' : '+');
+		for (i = SP_FBITS - 1; i >= 0; i--)
+			printk("%c", SPMANT(x) & SP_MBIT(i) ? '1' : '0');
+		printk("e%d", SPBEXP(x) - SP_EBIAS);
+		break;
+	case IEEE754_CLASS_NORM:
+		printk("%c1.", SPSIGN(x) ? '-' : '+');
+		for (i = SP_FBITS - 1; i >= 0; i--)
+			printk("%c", SPMANT(x) & SP_MBIT(i) ? '1' : '0');
+		printk("e%d", SPBEXP(x) - SP_EBIAS);
+		break;
+	default:
+		printk("Illegal/Unknown IEEE754 value class");
+	}
+	printk("\n");
+	return x;
+}