In 28aaa9c39945 ("kthread: consolidate kthread exit paths to prevent use-after-free")
we folded kthread_exit() into do_exit() when we fixed a nasty UAF bug.
We left kthread_exit() around as an alias to do_exit(). Remove it
completely.

Reported-by: Christian Loehle <christian.loehle@arm.com>
Link: https://lore.kernel.org/1ff1bce2-8bb4-463c-a631-16e14f4ea7e2@arm.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 include/linux/kthread.h    | 1 -
 include/linux/module.h     | 2 +-
 include/linux/sunrpc/svc.h | 2 +-
 kernel/kthread.c           | 8 ++++----
 kernel/module/main.c       | 2 +-
 lib/kunit/try-catch.c      | 2 +-
 tools/objtool/noreturns.h  | 1 -
 7 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index a01a474719a7..37982eca94f1 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -116,7 +116,6 @@ void *kthread_probe_data(struct task_struct *k);
 int kthread_park(struct task_struct *k);
 void kthread_unpark(struct task_struct *k);
 void kthread_parkme(void);
-#define kthread_exit(result) do_exit(result)
 void kthread_complete_and_exit(struct completion *, long) __noreturn;
 int kthreads_update_housekeeping(void);
 void kthread_do_exit(struct kthread *, long);
diff --git a/include/linux/module.h b/include/linux/module.h
index 14f391b186c6..79ac4a700b39 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -855,7 +855,7 @@ static inline int unregister_module_notifier(struct notifier_block *nb)
 	return 0;
 }
 
-#define module_put_and_kthread_exit(code) kthread_exit(code)
+#define module_put_and_kthread_exit(code) do_exit(code)
 
 static inline void print_modules(void)
 {
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 4dc14c7a711b..c86fc8a87eae 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -338,7 +338,7 @@ static inline void svc_thread_init_status(struct svc_rqst *rqstp, int err)
 {
 	store_release_wake_up(&rqstp->rq_err, err);
 	if (err)
-		kthread_exit(1);
+		do_exit(1);
 }
 
 struct svc_deferred_req {
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 791210daf8b4..1447c14c8540 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -323,7 +323,7 @@ void __noreturn kthread_complete_and_exit(struct completion *comp, long code)
 	if (comp)
 		complete(comp);
 
-	kthread_exit(code);
+	do_exit(code);
 }
 EXPORT_SYMBOL(kthread_complete_and_exit);
 
@@ -395,7 +395,7 @@ static int kthread(void *_create)
 	if (!done) {
 		kfree(create->full_name);
 		kfree(create);
-		kthread_exit(-EINTR);
+		do_exit(-EINTR);
 	}
 
 	self->full_name = create->full_name;
@@ -435,7 +435,7 @@ static int kthread(void *_create)
 		__kthread_parkme(self);
 		ret = threadfn(data);
 	}
-	kthread_exit(ret);
+	do_exit(ret);
 }
 
 /* called from kernel_clone() to get node information for about to be created task */
@@ -738,7 +738,7 @@ EXPORT_SYMBOL_GPL(kthread_park);
  * instead of calling wake_up_process(): the thread will exit without
  * calling threadfn().
  *
- * If threadfn() may call kthread_exit() itself, the caller must ensure
+ * If threadfn() may call do_exit() itself, the caller must ensure
  * task_struct can't go away.
  *
  * Returns the result of threadfn(), or %-EINTR if wake_up_process()
diff --git a/kernel/module/main.c b/kernel/module/main.c
index c3ce106c70af..340b4dc5c692 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -228,7 +228,7 @@ static int mod_strncmp(const char *str_a, const char *str_b, size_t n)
 void __noreturn __module_put_and_kthread_exit(struct module *mod, long code)
 {
 	module_put(mod);
-	kthread_exit(code);
+	do_exit(code);
 }
 EXPORT_SYMBOL(__module_put_and_kthread_exit);
 
diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
index d84a879f0a78..99d9603a2cfd 100644
--- a/lib/kunit/try-catch.c
+++ b/lib/kunit/try-catch.c
@@ -18,7 +18,7 @@
 void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)
 {
 	try_catch->try_result = -EFAULT;
-	kthread_exit(0);
+	do_exit(0);
 }
 EXPORT_SYMBOL_GPL(kunit_try_catch_throw);
 
diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h
index 14f8ab653449..40c0b05c6726 100644
--- a/tools/objtool/noreturns.h
+++ b/tools/objtool/noreturns.h
@@ -30,7 +30,6 @@ NORETURN(ex_handler_msr_mce)
 NORETURN(hlt_play_dead)
 NORETURN(hv_ghcb_terminate)
 NORETURN(kthread_complete_and_exit)
-NORETURN(kthread_exit)
 NORETURN(kunit_try_catch_throw)
 NORETURN(machine_real_restart)
 NORETURN(make_task_dead)

-- 
2.47.3

On Tue, 10 Mar 2026 15:56:09 +0100
Christian Brauner <brauner@kernel.org> wrote:

> In 28aaa9c39945 ("kthread: consolidate kthread exit paths to prevent use-after-free")
> we folded kthread_exit() into do_exit() when we fixed a nasty UAF bug.
> We left kthread_exit() around as an alias to do_exit(). Remove it
> completely.
...
> -#define module_put_and_kthread_exit(code) kthread_exit(code)
> +#define module_put_and_kthread_exit(code) do_exit(code)

I'm intrigued...
How does that actually know to do the module_put()?
(I know it does one - otherwise my driver wouldn't unload.)

The corresponding try_module_get(THIS_MODULE) is done before the
kthread_run() (and has to be 'put' if that fails).
So there is an explicit 'get' but an implicit 'put'.

While a loadable module that creates a kthread usually needs to give
the kthread a reference to its module and then have that reference
released as the kthread exits, I can imagine cases where that isn't true.
(Or broken code that just hopes the module won't be unloaded just
as the kthread exits.)

It actually makes me think that module_put_and_exit() ought to have
a 'module' parameter.
Or, perhaps, kthread_create() should have the module parameter and
hold a reference to that module until it exits.

	David

On Wed, 11 Mar 2026 10:47:36 +0000
David Laight <david.laight.linux@gmail.com> wrote:

> > -#define module_put_and_kthread_exit(code) kthread_exit(code)
> > +#define module_put_and_kthread_exit(code) do_exit(code)  
> 
> I'm intrigued...
> How does that actually know to do the module_put()?
> (I know it does one - otherwise my driver wouldn't unload.)

It's in the !CONFIG_MODULES section. No module_put() necessary. Only the
kthread_exit (do_exit) is needed.

-- Steve

Le Tue, Mar 10, 2026 at 03:56:09PM +0100, Christian Brauner a écrit :
> In 28aaa9c39945 ("kthread: consolidate kthread exit paths to prevent use-after-free")
> we folded kthread_exit() into do_exit() when we fixed a nasty UAF bug.
> We left kthread_exit() around as an alias to do_exit(). Remove it
> completely.

Thanks for fixing that UAF! I unfortunately missed it.

> 
> Reported-by: Christian Loehle <christian.loehle@arm.com>
> Link: https://lore.kernel.org/1ff1bce2-8bb4-463c-a631-16e14f4ea7e2@arm.com
> Signed-off-by: Christian Brauner <brauner@kernel.org>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

-- 
Frederic Weisbecker
SUSE Labs