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, 50 insertions, 0 deletions

diff --git a/rust/helpers/mm.c b/rust/helpers/mm.c
new file mode 100644
index 000000000..b5540997b
--- /dev/null
+++ b/rust/helpers/mm.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+
+__rust_helper void rust_helper_mmgrab(struct mm_struct *mm)
+{
+	mmgrab(mm);
+}
+
+__rust_helper void rust_helper_mmdrop(struct mm_struct *mm)
+{
+	mmdrop(mm);
+}
+
+__rust_helper void rust_helper_mmget(struct mm_struct *mm)
+{
+	mmget(mm);
+}
+
+__rust_helper bool rust_helper_mmget_not_zero(struct mm_struct *mm)
+{
+	return mmget_not_zero(mm);
+}
+
+__rust_helper void rust_helper_mmap_read_lock(struct mm_struct *mm)
+{
+	mmap_read_lock(mm);
+}
+
+__rust_helper bool rust_helper_mmap_read_trylock(struct mm_struct *mm)
+{
+	return mmap_read_trylock(mm);
+}
+
+__rust_helper void rust_helper_mmap_read_unlock(struct mm_struct *mm)
+{
+	mmap_read_unlock(mm);
+}
+
+__rust_helper struct vm_area_struct *
+rust_helper_vma_lookup(struct mm_struct *mm, unsigned long addr)
+{
+	return vma_lookup(mm, addr);
+}
+
+__rust_helper void rust_helper_vma_end_read(struct vm_area_struct *vma)
+{
+	vma_end_read(vma);
+}