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, 125 insertions, 0 deletions

diff --git a/fs/jfs/jfs_unicode.c b/fs/jfs/jfs_unicode.c
new file mode 100644
index 000000000..0c1e90272
--- /dev/null
+++ b/fs/jfs/jfs_unicode.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) International Business Machines Corp., 2000-2004
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include "jfs_incore.h"
+#include "jfs_filsys.h"
+#include "jfs_unicode.h"
+#include "jfs_debug.h"
+
+/*
+ * NAME:	jfs_strfromUCS()
+ *
+ * FUNCTION:	Convert little-endian unicode string to character string
+ *
+ */
+int jfs_strfromUCS_le(char *to, const __le16 * from,
+		      int len, struct nls_table *codepage)
+{
+	int i;
+	int outlen = 0;
+	static int warn_again = 5;	/* Only warn up to 5 times total */
+	int warn = !!warn_again;	/* once per string */
+
+	if (codepage) {
+		for (i = 0; (i < len) && from[i]; i++) {
+			int charlen;
+			charlen =
+			    codepage->uni2char(le16_to_cpu(from[i]),
+					       &to[outlen],
+					       NLS_MAX_CHARSET_SIZE);
+			if (charlen > 0)
+				outlen += charlen;
+			else
+				to[outlen++] = '?';
+		}
+	} else {
+		for (i = 0; (i < len) && from[i]; i++) {
+			if (unlikely(le16_to_cpu(from[i]) & 0xff00)) {
+				to[i] = '?';
+				if (unlikely(warn)) {
+					warn--;
+					warn_again--;
+					printk(KERN_ERR
+			"non-latin1 character 0x%x found in JFS file name\n",
+					       le16_to_cpu(from[i]));
+					printk(KERN_ERR
+				"mount with iocharset=utf8 to access\n");
+				}
+
+			}
+			else
+				to[i] = (char) (le16_to_cpu(from[i]));
+		}
+		outlen = i;
+	}
+	to[outlen] = 0;
+	return outlen;
+}
+
+/*
+ * NAME:	jfs_strtoUCS()
+ *
+ * FUNCTION:	Convert character string to unicode string
+ *
+ */
+static int jfs_strtoUCS(wchar_t * to, const unsigned char *from, int len,
+		struct nls_table *codepage)
+{
+	int charlen;
+	int i;
+
+	if (codepage) {
+		for (i = 0; len && *from; i++, from += charlen, len -= charlen)
+		{
+			charlen = codepage->char2uni(from, len, &to[i]);
+			if (charlen < 1) {
+				jfs_err("jfs_strtoUCS: char2uni returned %d.",
+					charlen);
+				jfs_err("charset = %s, char = 0x%x",
+					codepage->charset, *from);
+				return charlen;
+			}
+		}
+	} else {
+		for (i = 0; (i < len) && from[i]; i++)
+			to[i] = (wchar_t) from[i];
+	}
+
+	to[i] = 0;
+	return i;
+}
+
+/*
+ * NAME:	get_UCSname()
+ *
+ * FUNCTION:	Allocate and translate to unicode string
+ *
+ */
+int get_UCSname(struct component_name * uniName, struct dentry *dentry)
+{
+	struct nls_table *nls_tab = JFS_SBI(dentry->d_sb)->nls_tab;
+	int length = dentry->d_name.len;
+
+	if (length > JFS_NAME_MAX)
+		return -ENAMETOOLONG;
+
+	uniName->name =
+	    kmalloc_array(length + 1, sizeof(wchar_t), GFP_NOFS);
+
+	if (uniName->name == NULL)
+		return -ENOMEM;
+
+	uniName->namlen = jfs_strtoUCS(uniName->name, dentry->d_name.name,
+				       length, nls_tab);
+
+	if (uniName->namlen < 0) {
+		kfree(uniName->name);
+		return uniName->namlen;
+	}
+
+	return 0;
+}