vhost_task_create() creates a task and keeps a reference to its
task_struct. That task may exit early via a signal and its task_struct
will be released.
A pending vhost_task_wake() will then attempt to wake the task and
access a task_struct which is no longer there.
Acquire a reference on the task_struct while creating the thread and
release the reference while the struct vhost_task itself is removed.
If the task exits early due to a signal, then the vhost_task_wake() will
still access a valid task_struct. The wake is safe and will be skipped
in this case.
Fixes: f9010dbdce911 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps
regression")
Reported-by: Sean Christopherson <sea...@google.com>
Closes: https://lore.kernel.org/all/akkletodxkxaa...@google.com/
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
---
kernel/vhost_task.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
index bc738fa90c1d6..27107dcc1cbfe 100644
--- a/kernel/vhost_task.c
+++ b/kernel/vhost_task.c
@@ -100,6 +100,7 @@ void vhost_task_stop(struct vhost_task *vtsk)
* freeing it below.
*/
wait_for_completion(&vtsk->exited);
+ put_task_struct(vtsk->task);
kfree(vtsk);
}
EXPORT_SYMBOL_GPL(vhost_task_stop);
@@ -148,7 +149,7 @@ struct vhost_task *vhost_task_create(bool (*fn)(void *),
return ERR_CAST(tsk);
}
- vtsk->task = tsk;
+ vtsk->task = get_task_struct(tsk);
return vtsk;
}
EXPORT_SYMBOL_GPL(vhost_task_create);
--
2.51.0
