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>

2 files changed, 35 insertions, 0 deletions

diff --git a/include/asm-generic/vdso/clocksource.h b/include/asm-generic/vdso/clocksource.h
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/include/asm-generic/vdso/clocksource.h
diff --git a/include/asm-generic/vdso/vsyscall.h b/include/asm-generic/vdso/vsyscall.h
new file mode 100644
index 000000000..a6b03cfba
--- /dev/null
+++ b/include/asm-generic/vdso/vsyscall.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_GENERIC_VSYSCALL_H
+#define __ASM_GENERIC_VSYSCALL_H
+
+#ifndef __ASSEMBLER__
+
+#ifndef __arch_get_vdso_u_time_data
+static __always_inline const struct vdso_time_data *__arch_get_vdso_u_time_data(void)
+{
+	return &vdso_u_time_data;
+}
+#endif
+
+#ifndef __arch_get_vdso_u_rng_data
+static __always_inline const struct vdso_rng_data *__arch_get_vdso_u_rng_data(void)
+{
+	return &vdso_u_rng_data;
+}
+#endif
+
+#ifndef __arch_update_vdso_clock
+static __always_inline void __arch_update_vdso_clock(struct vdso_clock *vc)
+{
+}
+#endif /* __arch_update_vdso_clock */
+
+#ifndef __arch_sync_vdso_time_data
+static __always_inline void __arch_sync_vdso_time_data(struct vdso_time_data *vdata)
+{
+}
+#endif /* __arch_sync_vdso_time_data */
+
+#endif /* !__ASSEMBLER__ */
+
+#endif /* __ASM_GENERIC_VSYSCALL_H */