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, 39 insertions, 0 deletions

diff --git a/fs/lockd/share.h b/fs/lockd/share.h
new file mode 100644
index 000000000..a12b6c454
--- /dev/null
+++ b/fs/lockd/share.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DOS share management for lockd.
+ *
+ * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
+ */
+
+#ifndef _LOCKD_SHARE_H
+#define _LOCKD_SHARE_H
+
+#include <linux/bits.h>
+
+/* Synthetic svid for lockowner lookup during share operations */
+#define LOCKD_SHARE_SVID	(~(u32)0)
+
+/* One bit per (access, deny) pair; index = (access << 2) | deny */
+#define LOCKD_FSH_BIT(a, d)	BIT(((a) << 2) | (d))
+
+/*
+ * DOS share for a specific file
+ */
+struct lockd_share {
+	struct lockd_share *	s_next;		/* linked list */
+	struct nlm_host *	s_host;		/* client host */
+	struct nlm_file *	s_file;		/* shared file */
+	struct xdr_netobj	s_owner;	/* owner handle */
+	u32			s_access;	/* access mode */
+	u32			s_mode;		/* deny mode */
+	u16			s_access_deny_bmap;	/* held (access, deny) pairs */
+};
+
+__be32	nlmsvc_share_file(struct nlm_host *host, struct nlm_file *file,
+			  struct xdr_netobj *oh, u32 access, u32 mode);
+__be32	nlmsvc_unshare_file(struct nlm_host *host, struct nlm_file *file,
+			    struct xdr_netobj *oh, u32 access, u32 mode);
+void	nlmsvc_traverse_shares(struct nlm_host *, struct nlm_file *,
+					       nlm_host_match_fn_t);
+
+#endif /* _LOCKD_SHARE_H */