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, 94 insertions, 0 deletions

diff --git a/arch/microblaze/lib/memset.c b/arch/microblaze/lib/memset.c
new file mode 100644
index 000000000..7c2352d56
--- /dev/null
+++ b/arch/microblaze/lib/memset.c
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
+ * Copyright (C) 2008-2009 PetaLogix
+ * Copyright (C) 2007 John Williams
+ *
+ * Reasonably optimised generic C-code for memset on Microblaze
+ * This is generic C code to do efficient, alignment-aware memcpy.
+ *
+ * It is based on demo code originally Copyright 2001 by Intel Corp, taken from
+ * http://www.embedded.com/showArticle.jhtml?articleID=19205567
+ *
+ * Attempts were made, unsuccessfully, to contact the original
+ * author of this code (Michael Morrow, Intel).  Below is the original
+ * copyright notice.
+ *
+ * This software has been developed by Intel Corporation.
+ * Intel specifically disclaims all warranties, express or
+ * implied, and all liability, including consequential and
+ * other indirect damages, for the use of this program, including
+ * liability for infringement of any proprietary rights,
+ * and including the warranties of merchantability and fitness
+ * for a particular purpose. Intel does not assume any
+ * responsibility for and errors which may appear in this program
+ * not any responsibility to update it.
+ */
+
+#include <linux/export.h>
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/compiler.h>
+#include <linux/string.h>
+
+#ifdef CONFIG_OPT_LIB_FUNCTION
+void *memset(void *v_src, int c, __kernel_size_t n)
+{
+	char *src = v_src;
+	uint32_t *i_src;
+	uint32_t w32 = 0;
+
+	/* Truncate c to 8 bits */
+	c = (c & 0xFF);
+
+	if (unlikely(c)) {
+		/* Make a repeating word out of it */
+		w32 = c;
+		w32 |= w32 << 8;
+		w32 |= w32 << 16;
+	}
+
+	if (likely(n >= 4)) {
+		/* Align the destination to a word boundary */
+		/* This is done in an endian independent manner */
+		switch ((unsigned) src & 3) {
+		case 1:
+			*src++ = c;
+			--n;
+			fallthrough;
+		case 2:
+			*src++ = c;
+			--n;
+			fallthrough;
+		case 3:
+			*src++ = c;
+			--n;
+		}
+
+		i_src  = (void *)src;
+
+		/* Do as many full-word copies as we can */
+		for (; n >= 4; n -= 4)
+			*i_src++ = w32;
+
+		src  = (void *)i_src;
+	}
+
+	/* Simple, byte oriented memset or the rest of count. */
+	switch (n) {
+	case 3:
+		*src++ = c;
+		fallthrough;
+	case 2:
+		*src++ = c;
+		fallthrough;
+	case 1:
+		*src++ = c;
+		break;
+	default:
+		break;
+	}
+
+	return v_src;
+}
+EXPORT_SYMBOL(memset);
+#endif /* CONFIG_OPT_LIB_FUNCTION */