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, 25 insertions, 0 deletions

diff --git a/fs/smb/client/smb1debug.c b/fs/smb/client/smb1debug.c
new file mode 100644
index 000000000..e2d013e75
--- /dev/null
+++ b/fs/smb/client/smb1debug.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *   Copyright (C) International Business Machines  Corp., 2000,2005
+ *
+ *   Modified by Steve French (sfrench@us.ibm.com)
+ */
+#include "cifsproto.h"
+#include "smb1proto.h"
+#include "cifs_debug.h"
+
+void cifs_dump_detail(void *buf, size_t buf_len, struct TCP_Server_Info *server)
+{
+#ifdef CONFIG_CIFS_DEBUG2
+	struct smb_hdr *smb = buf;
+
+	cifs_dbg(VFS, "Cmd: %d Err: 0x%x Flags: 0x%x Flgs2: 0x%x Mid: %d Pid: %d Wct: %d\n",
+		 smb->Command, smb->Status.CifsError, smb->Flags,
+		 smb->Flags2, smb->Mid, smb->Pid, smb->WordCount);
+	if (!server->ops->check_message(buf, buf_len, server->total_read, server)) {
+		cifs_dbg(VFS, "smb buf %p len %u\n", smb,
+			 server->ops->calc_smb_size(smb));
+	}
+#endif /* CONFIG_CIFS_DEBUG2 */
+}