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, 47 insertions, 0 deletions

diff --git a/drivers/nvme/target/debugfs.h b/drivers/nvme/target/debugfs.h
new file mode 100644
index 000000000..b559d254f
--- /dev/null
+++ b/drivers/nvme/target/debugfs.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DebugFS interface for the NVMe target.
+ * Copyright (c) 2022-2024 Shadow
+ * Copyright (c) 2024 SUSE LLC
+ */
+#ifndef NVMET_DEBUGFS_H
+#define NVMET_DEBUGFS_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_NVME_TARGET_DEBUGFS
+int nvmet_debugfs_subsys_setup(struct nvmet_subsys *subsys);
+void nvmet_debugfs_subsys_free(struct nvmet_subsys *subsys);
+int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl);
+void nvmet_debugfs_ctrl_free(struct nvmet_ctrl *ctrl);
+void nvmet_debugfs_ns_setup(struct nvmet_ns *ns);
+void nvmet_debugfs_ns_free(struct nvmet_ns *ns);
+
+int __init nvmet_init_debugfs(void);
+void nvmet_exit_debugfs(void);
+#else
+static inline int nvmet_debugfs_subsys_setup(struct nvmet_subsys *subsys)
+{
+	return 0;
+}
+static inline void nvmet_debugfs_subsys_free(struct nvmet_subsys *subsys){}
+
+static inline int nvmet_debugfs_ctrl_setup(struct nvmet_ctrl *ctrl)
+{
+	return 0;
+}
+static inline void nvmet_debugfs_ctrl_free(struct nvmet_ctrl *ctrl) {}
+
+static inline void nvmet_debugfs_ns_setup(struct nvmet_ns *ns) {}
+static inline void nvmet_debugfs_ns_free(struct nvmet_ns *ns) {}
+
+static inline int __init nvmet_init_debugfs(void)
+{
+    return 0;
+}
+
+static inline void nvmet_exit_debugfs(void) {}
+
+#endif
+
+#endif /* NVMET_DEBUGFS_H */