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, 70 insertions, 0 deletions

diff --git a/fs/verity/init.c b/fs/verity/init.c
new file mode 100644
index 000000000..3aa55dec8
--- /dev/null
+++ b/fs/verity/init.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs-verity module initialization and logging
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#define CREATE_TRACE_POINTS
+#include "fsverity_private.h"
+
+#include <linux/ratelimit.h>
+
+#ifdef CONFIG_SYSCTL
+static const struct ctl_table fsverity_sysctl_table[] = {
+#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
+	{
+		.procname       = "require_signatures",
+		.data           = &fsverity_require_signatures,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec_minmax,
+		.extra1         = SYSCTL_ZERO,
+		.extra2         = SYSCTL_ONE,
+	},
+#endif
+};
+
+static void __init fsverity_init_sysctl(void)
+{
+	register_sysctl_init("fs/verity", fsverity_sysctl_table);
+}
+#else /* CONFIG_SYSCTL */
+static inline void fsverity_init_sysctl(void)
+{
+}
+#endif /* !CONFIG_SYSCTL */
+
+void fsverity_msg(const struct inode *inode, const char *level,
+		  const char *fmt, ...)
+{
+	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+	struct va_format vaf;
+	va_list args;
+
+	if (!__ratelimit(&rs))
+		return;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	if (inode)
+		printk("%sfs-verity (%s, inode %llu): %pV\n",
+		       level, inode->i_sb->s_id, inode->i_ino, &vaf);
+	else
+		printk("%sfs-verity: %pV\n", level, &vaf);
+	va_end(args);
+}
+
+static int __init fsverity_init(void)
+{
+	fsverity_check_hash_algs();
+	fsverity_init_info_cache();
+	fsverity_init_workqueue();
+	fsverity_init_sysctl();
+	fsverity_init_signature();
+	fsverity_init_bpf();
+	return 0;
+}
+late_initcall(fsverity_init)