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, 41 insertions, 0 deletions

diff --git a/net/Kconfig.debug b/net/Kconfig.debug
new file mode 100644
index 000000000..277fab8c4
--- /dev/null
+++ b/net/Kconfig.debug
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config NET_DEV_REFCNT_TRACKER
+	bool "Enable net device refcount tracking"
+	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT && NET
+	select REF_TRACKER
+	default n
+	help
+	  Enable debugging feature to track device references.
+	  This adds memory and cpu costs.
+
+config NET_NS_REFCNT_TRACKER
+	bool "Enable networking namespace refcount tracking"
+	depends on DEBUG_KERNEL && STACKTRACE_SUPPORT && NET
+	select REF_TRACKER
+	default n
+	help
+	  Enable debugging feature to track netns references.
+	  This adds memory and cpu costs.
+
+config DEBUG_NET
+	bool "Add generic networking debug"
+	depends on DEBUG_KERNEL && NET
+	help
+	  Enable extra sanity checks in networking.
+	  This is mostly used by fuzzers, but is safe to select.
+
+config DEBUG_NET_SMALL_RTNL
+	bool "Add extra per-netns mutex inside RTNL"
+	depends on DEBUG_KERNEL && NET && LOCK_DEBUGGING_SUPPORT
+	select PROVE_LOCKING
+	default n
+	help
+	  rtnl_lock() is being replaced with rtnl_net_lock() that
+	  acquires the global RTNL and a small per-netns RTNL mutex.
+
+	  During the conversion, rtnl_net_lock() just adds an extra
+	  mutex in every RTNL scope and slows down the operations.
+
+	  Once the conversion completes, rtnl_lock() will be removed
+	  and rtnetlink will gain per-netns scalability.