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, 51 insertions, 0 deletions

diff --git a/fs/jffs2/writev.c b/fs/jffs2/writev.c
new file mode 100644
index 000000000..a1bda9dab
--- /dev/null
+++ b/fs/jffs2/writev.c
@@ -0,0 +1,51 @@
+/*
+ * JFFS2 -- Journalling Flash File System, Version 2.
+ *
+ * Copyright © 2001-2007 Red Hat, Inc.
+ *
+ * Created by David Woodhouse <dwmw2@infradead.org>
+ *
+ * For licensing information, see the file 'LICENCE' in this directory.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/mtd/mtd.h>
+#include "nodelist.h"
+
+int jffs2_flash_direct_writev(struct jffs2_sb_info *c, const struct kvec *vecs,
+			      unsigned long count, loff_t to, size_t *retlen)
+{
+	if (!jffs2_is_writebuffered(c)) {
+		if (jffs2_sum_active()) {
+			int res;
+			res = jffs2_sum_add_kvec(c, vecs, count, (uint32_t) to);
+			if (res) {
+				return res;
+			}
+		}
+	}
+
+	return mtd_writev(c->mtd, vecs, count, to, retlen);
+}
+
+int jffs2_flash_direct_write(struct jffs2_sb_info *c, loff_t ofs, size_t len,
+			size_t *retlen, const u_char *buf)
+{
+	int ret;
+	ret = mtd_write(c->mtd, ofs, len, retlen, buf);
+
+	if (jffs2_sum_active()) {
+		struct kvec vecs[1];
+		int res;
+
+		vecs[0].iov_base = (unsigned char *) buf;
+		vecs[0].iov_len = len;
+
+		res = jffs2_sum_add_kvec(c, vecs, 1, (uint32_t) ofs);
+		if (res) {
+			return res;
+		}
+	}
+	return ret;
+}