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, 74 insertions, 0 deletions

diff --git a/arch/m68k/lib/memset.c b/arch/m68k/lib/memset.c
new file mode 100644
index 000000000..8a7639f0a
--- /dev/null
+++ b/arch/m68k/lib/memset.c
@@ -0,0 +1,74 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/string.h>
+
+void *memset(void *s, int c, size_t count)
+{
+	void *xs = s;
+	size_t temp;
+
+	if (!count)
+		return xs;
+	c &= 0xff;
+	c |= c << 8;
+	c |= c << 16;
+	if ((long)s & 1) {
+		char *cs = s;
+		*cs++ = c;
+		s = cs;
+		count--;
+	}
+	if (count > 2 && (long)s & 2) {
+		short *ss = s;
+		*ss++ = c;
+		s = ss;
+		count -= 2;
+	}
+	temp = count >> 2;
+	if (temp) {
+		long *ls = s;
+#if defined(CONFIG_M68000) || defined(CONFIG_COLDFIRE)
+		for (; temp; temp--)
+			*ls++ = c;
+#else
+		size_t temp1;
+		asm volatile (
+			"	movel %1,%2\n"
+			"	andw  #7,%2\n"
+			"	lsrl  #3,%1\n"
+			"	negw  %2\n"
+			"	jmp   %%pc@(2f,%2:w:2)\n"
+			"1:	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"	movel %3,%0@+\n"
+			"2:	dbra  %1,1b\n"
+			"	clrw  %1\n"
+			"	subql #1,%1\n"
+			"	jpl   1b"
+			: "=a" (ls), "=d" (temp), "=&d" (temp1)
+			: "d" (c), "0" (ls), "1" (temp));
+#endif
+		s = ls;
+	}
+	if (count & 2) {
+		short *ss = s;
+		*ss++ = c;
+		s = ss;
+	}
+	if (count & 1) {
+		char *cs = s;
+		*cs = c;
+	}
+	return xs;
+}
+EXPORT_SYMBOL(memset);