ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 123 insertions, 0 deletions

diff --git a/tools/bpf/bpftool/iter.c b/tools/bpf/bpftool/iter.c
new file mode 100644
index 000000000..df5f0d1e0
--- /dev/null
+++ b/tools/bpf/bpftool/iter.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+// Copyright (C) 2020 Facebook
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <errno.h>
+#include <unistd.h>
+#include <linux/err.h>
+#include <bpf/libbpf.h>
+
+#include "main.h"
+
+static int do_pin(int argc, char **argv)
+{
+	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, iter_opts);
+	union bpf_iter_link_info linfo;
+	const char *objfile, *path;
+	struct bpf_program *prog;
+	struct bpf_object *obj;
+	struct bpf_link *link;
+	int err = -1, map_fd = -1;
+
+	if (!REQ_ARGS(2))
+		usage();
+
+	objfile = GET_ARG();
+	path = GET_ARG();
+
+	/* optional arguments */
+	if (argc) {
+		if (is_prefix(*argv, "map")) {
+			NEXT_ARG();
+
+			if (!REQ_ARGS(2)) {
+				p_err("incorrect map spec");
+				return -1;
+			}
+
+			map_fd = map_parse_fd(&argc, &argv, BPF_F_RDONLY);
+			if (map_fd < 0)
+				return -1;
+
+			memset(&linfo, 0, sizeof(linfo));
+			linfo.map.map_fd = map_fd;
+			iter_opts.link_info = &linfo;
+			iter_opts.link_info_len = sizeof(linfo);
+		}
+	}
+
+	obj = bpf_object__open(objfile);
+	if (!obj) {
+		err = -errno;
+		p_err("can't open objfile %s", objfile);
+		goto close_map_fd;
+	}
+
+	err = bpf_object__load(obj);
+	if (err) {
+		p_err("can't load objfile %s", objfile);
+		goto close_obj;
+	}
+
+	prog = bpf_object__next_program(obj, NULL);
+	if (!prog) {
+		err = -errno;
+		p_err("can't find bpf program in objfile %s", objfile);
+		goto close_obj;
+	}
+
+	link = bpf_program__attach_iter(prog, &iter_opts);
+	if (!link) {
+		err = -errno;
+		p_err("attach_iter failed for program %s",
+		      bpf_program__name(prog));
+		goto close_obj;
+	}
+
+	err = mount_bpffs_for_file(path);
+	if (err)
+		goto close_link;
+
+	err = bpf_link__pin(link, path);
+	if (err) {
+		p_err("pin_iter failed for program %s to path %s",
+		      bpf_program__name(prog), path);
+		goto close_link;
+	}
+
+close_link:
+	bpf_link__destroy(link);
+close_obj:
+	bpf_object__close(obj);
+close_map_fd:
+	if (map_fd >= 0)
+		close(map_fd);
+	return err;
+}
+
+static int do_help(int argc, char **argv)
+{
+	fprintf(stderr,
+		"Usage: %1$s %2$s pin OBJ PATH [map MAP]\n"
+		"       %1$s %2$s help\n"
+		"\n"
+		"       " HELP_SPEC_MAP "\n"
+		"       " HELP_SPEC_OPTIONS " }\n"
+		"",
+		bin_name, "iter");
+
+	return 0;
+}
+
+static const struct cmd cmds[] = {
+	{ "help",	do_help },
+	{ "pin",	do_pin },
+	{ 0 }
+};
+
+int do_iter(int argc, char **argv)
+{
+	return cmd_select(cmds, argc, argv, do_help);
+}