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, 83 insertions, 0 deletions

diff --git a/arch/mips/math-emu/ieee754.c b/arch/mips/math-emu/ieee754.c
new file mode 100644
index 000000000..0ba5dfbd4
--- /dev/null
+++ b/arch/mips/math-emu/ieee754.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* ieee754 floating point arithmetic
+ * single and double precision
+ *
+ * BUGS
+ * not much dp done
+ * doesn't generate IEEE754_INEXACT
+ */
+/*
+ * MIPS floating point support
+ * Copyright (C) 1994-2000 Algorithmics Ltd.
+ */
+
+#include <linux/compiler.h>
+
+#include "ieee754.h"
+#include "ieee754sp.h"
+#include "ieee754dp.h"
+
+/*
+ * Special constants
+ */
+
+/*
+ * Older GCC requires the inner braces for initialization of union ieee754dp's
+ * anonymous struct member.  Without an error will result.
+ */
+#define xPCNST(s, b, m, ebias)						\
+{									\
+	{								\
+		.sign	= (s),						\
+		.bexp	= (b) + ebias,					\
+		.mant	= (m)						\
+	}								\
+}
+
+#define DPCNST(s, b, m)							\
+	xPCNST(s, b, m, DP_EBIAS)
+
+const union ieee754dp __ieee754dp_spcvals[] = {
+	DPCNST(0, DP_EMIN - 1, 0x0000000000000ULL),	/* + zero   */
+	DPCNST(1, DP_EMIN - 1, 0x0000000000000ULL),	/* - zero   */
+	DPCNST(0, 0,	       0x0000000000000ULL),	/* + 1.0   */
+	DPCNST(1, 0,	       0x0000000000000ULL),	/* - 1.0   */
+	DPCNST(0, 3,           0x4000000000000ULL),	/* + 10.0   */
+	DPCNST(1, 3,           0x4000000000000ULL),	/* - 10.0   */
+	DPCNST(0, DP_EMAX + 1, 0x0000000000000ULL),	/* + infinity */
+	DPCNST(1, DP_EMAX + 1, 0x0000000000000ULL),	/* - infinity */
+	DPCNST(0, DP_EMAX + 1, 0x7FFFFFFFFFFFFULL),	/* + ind legacy qNaN */
+	DPCNST(0, DP_EMAX + 1, 0x8000000000000ULL),	/* + indef 2008 qNaN */
+	DPCNST(0, DP_EMAX,     0xFFFFFFFFFFFFFULL),	/* + max */
+	DPCNST(1, DP_EMAX,     0xFFFFFFFFFFFFFULL),	/* - max */
+	DPCNST(0, DP_EMIN,     0x0000000000000ULL),	/* + min normal */
+	DPCNST(1, DP_EMIN,     0x0000000000000ULL),	/* - min normal */
+	DPCNST(0, DP_EMIN - 1, 0x0000000000001ULL),	/* + min denormal */
+	DPCNST(1, DP_EMIN - 1, 0x0000000000001ULL),	/* - min denormal */
+	DPCNST(0, 31,          0x0000000000000ULL),	/* + 1.0e31 */
+	DPCNST(0, 63,          0x0000000000000ULL),	/* + 1.0e63 */
+};
+
+#define SPCNST(s, b, m)							\
+	xPCNST(s, b, m, SP_EBIAS)
+
+const union ieee754sp __ieee754sp_spcvals[] = {
+	SPCNST(0, SP_EMIN - 1, 0x000000),	/* + zero   */
+	SPCNST(1, SP_EMIN - 1, 0x000000),	/* - zero   */
+	SPCNST(0, 0,	       0x000000),	/* + 1.0   */
+	SPCNST(1, 0,	       0x000000),	/* - 1.0   */
+	SPCNST(0, 3,	       0x200000),	/* + 10.0   */
+	SPCNST(1, 3,	       0x200000),	/* - 10.0   */
+	SPCNST(0, SP_EMAX + 1, 0x000000),	/* + infinity */
+	SPCNST(1, SP_EMAX + 1, 0x000000),	/* - infinity */
+	SPCNST(0, SP_EMAX + 1, 0x3FFFFF),	/* + indef legacy quiet NaN */
+	SPCNST(0, SP_EMAX + 1, 0x400000),	/* + indef 2008 quiet NaN */
+	SPCNST(0, SP_EMAX,     0x7FFFFF),	/* + max normal */
+	SPCNST(1, SP_EMAX,     0x7FFFFF),	/* - max normal */
+	SPCNST(0, SP_EMIN,     0x000000),	/* + min normal */
+	SPCNST(1, SP_EMIN,     0x000000),	/* - min normal */
+	SPCNST(0, SP_EMIN - 1, 0x000001),	/* + min denormal */
+	SPCNST(1, SP_EMIN - 1, 0x000001),	/* - min denormal */
+	SPCNST(0, 31,	       0x000000),	/* + 1.0e31 */
+	SPCNST(0, 63,	       0x000000),	/* + 1.0e63 */
+};