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, 83 insertions, 0 deletions

diff --git a/fs/smb/client/smbencrypt.c b/fs/smb/client/smbencrypt.c
new file mode 100644
index 000000000..094b8296d
--- /dev/null
+++ b/fs/smb/client/smbencrypt.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+   Unix SMB/Netbios implementation.
+   Version 1.9.
+   SMB parameters and setup
+   Copyright (C) Andrew Tridgell 1992-2000
+   Copyright (C) Luke Kenneth Casson Leighton 1996-2000
+   Modified by Jeremy Allison 1995.
+   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
+   Modified by Steve French (sfrench@us.ibm.com) 2002-2003
+
+*/
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/fips.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/random.h>
+#include "cifs_fs_sb.h"
+#include "cifs_unicode.h"
+#include "cifsglob.h"
+#include "cifs_debug.h"
+#include "cifsproto.h"
+#include "../common/md4.h"
+
+/* following came from the other byteorder.h to avoid include conflicts */
+#define CVAL(buf,pos) (((unsigned char *)(buf))[pos])
+#define SSVALX(buf,pos,val) (CVAL(buf,pos)=(val)&0xFF,CVAL(buf,pos+1)=(val)>>8)
+#define SSVAL(buf,pos,val) SSVALX((buf),(pos),((__u16)(val)))
+
+/* produce a md4 message digest from data of length n bytes */
+static int
+mdfour(unsigned char *md4_hash, unsigned char *link_str, int link_len)
+{
+	int rc;
+	struct md4_ctx mctx;
+
+	rc = cifs_md4_init(&mctx);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not init MD4\n", __func__);
+		goto mdfour_err;
+	}
+	rc = cifs_md4_update(&mctx, link_str, link_len);
+	if (rc) {
+		cifs_dbg(VFS, "%s: Could not update MD4\n", __func__);
+		goto mdfour_err;
+	}
+	rc = cifs_md4_final(&mctx, md4_hash);
+	if (rc)
+		cifs_dbg(VFS, "%s: Could not finalize MD4\n", __func__);
+
+
+mdfour_err:
+	return rc;
+}
+
+/*
+ * Creates the MD4 Hash of the users password in NT UNICODE.
+ */
+
+int
+E_md4hash(const unsigned char *passwd, unsigned char *p16,
+	const struct nls_table *codepage)
+{
+	int rc;
+	int len;
+	__le16 wpwd[129];
+
+	/* Password cannot be longer than 128 characters */
+	if (passwd) /* Password must be converted to NT unicode */
+		len = cifs_strtoUTF16(wpwd, passwd, 128, codepage);
+	else {
+		len = 0;
+		*wpwd = 0; /* Ensure string is null terminated */
+	}
+
+	rc = mdfour(p16, (unsigned char *) wpwd, len * sizeof(__le16));
+	memzero_explicit(wpwd, sizeof(wpwd));
+
+	return rc;
+}