From: Stefan Metzmacher <metze@samba.org>
Date: Sat, 24 Apr 2021 23:26:03 +0000 (+0200)
Subject: kernel: always initialize task->pf_io_worker to NULL
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=ff244303301f6f2ac90107c61d18826efd0af822;p=linux.git

kernel: always initialize task->pf_io_worker to NULL

Otherwise io_wq_worker_{running,sleeping}() may dereference an
invalid pointer (in future). Currently all users of create_io_thread()
are fine and get task->pf_io_worker = NULL implicitly from the
wq_manager, which got it either from the userspace thread
of the sq_thread, which explicitly reset it to NULL.

I think it's safer to always reset it in order to avoid future
problems.

Fixes: 3bfe6106693b ("io-wq: fork worker threads from original task")
cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/kernel/fork.c b/kernel/fork.c
index b81ccb1ca3a7d..224c8317df342 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -927,6 +927,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	tsk->splice_pipe = NULL;
 	tsk->task_frag.page = NULL;
 	tsk->wake_q.next = NULL;
+	tsk->pf_io_worker = NULL;
 
 	account_kernel_stack(tsk, 1);