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, 75 insertions, 0 deletions

diff --git a/fs/minix/itree_v2.c b/fs/minix/itree_v2.c
new file mode 100644
index 000000000..9d00f31a2
--- /dev/null
+++ b/fs/minix/itree_v2.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/buffer_head.h>
+#include "minix.h"
+
+enum {DIRECT = 7, DEPTH = 4};	/* Have triple indirect */
+
+typedef u32 block_t;	/* 32 bit, host order */
+
+static inline unsigned long block_to_cpu(block_t n)
+{
+	return n;
+}
+
+static inline block_t cpu_to_block(unsigned long n)
+{
+	return n;
+}
+
+static inline block_t *i_data(struct inode *inode)
+{
+	return (block_t *)minix_i(inode)->u.i2_data;
+}
+
+#define DIRCOUNT 7
+#define INDIRCOUNT(sb) (1 << ((sb)->s_blocksize_bits - 2))
+
+static int block_to_path(struct inode * inode, long block, int offsets[DEPTH])
+{
+	int n = 0;
+	struct super_block *sb = inode->i_sb;
+
+	if (block < 0) {
+		printk("MINIX-fs: block_to_path: block %ld < 0 on dev %pg\n",
+			block, sb->s_bdev);
+		return 0;
+	}
+	if ((u64)block * (u64)sb->s_blocksize >= sb->s_maxbytes)
+		return 0;
+
+	if (block < DIRCOUNT) {
+		offsets[n++] = block;
+	} else if ((block -= DIRCOUNT) < INDIRCOUNT(sb)) {
+		offsets[n++] = DIRCOUNT;
+		offsets[n++] = block;
+	} else if ((block -= INDIRCOUNT(sb)) < INDIRCOUNT(sb) * INDIRCOUNT(sb)) {
+		offsets[n++] = DIRCOUNT + 1;
+		offsets[n++] = block / INDIRCOUNT(sb);
+		offsets[n++] = block % INDIRCOUNT(sb);
+	} else {
+		block -= INDIRCOUNT(sb) * INDIRCOUNT(sb);
+		offsets[n++] = DIRCOUNT + 2;
+		offsets[n++] = (block / INDIRCOUNT(sb)) / INDIRCOUNT(sb);
+		offsets[n++] = (block / INDIRCOUNT(sb)) % INDIRCOUNT(sb);
+		offsets[n++] = block % INDIRCOUNT(sb);
+	}
+	return n;
+}
+
+#include "itree_common.c"
+
+int V2_minix_get_block(struct inode * inode, long block,
+			struct buffer_head *bh_result, int create)
+{
+	return get_block(inode, block, bh_result, create);
+}
+
+void V2_minix_truncate(struct inode * inode)
+{
+	truncate(inode);
+}
+
+unsigned V2_minix_blocks(loff_t size, struct super_block *sb)
+{
+	return nblocks(size, sb);
+}