io_uring/io-wq: only free worker if it was allocated for creation

commit e6db6f9398dadcbc06318a133d4c44a2d3844e61 upstream.

We have two types of task_work based creation, one is using an existing
worker to setup a new one (eg when going to sleep and we have no free
workers), and the other is allocating a new worker. Only the latter
should be freed when we cancel task_work creation for a new worker.

Fixes: af82425c6a2d ("io_uring/io-wq: free worker if task_work creation is canceled")
Reported-by: syzbot+d56ec896af3637bdb7e4@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index 992dcd9..411bb2d 100644 (file)
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -1230,7 +1230,12 @@ static void io_wq_cancel_tw_create(struct io_wq *wq)
 
                worker = container_of(cb, struct io_worker, create_work);
                io_worker_cancel_cb(worker);
-               kfree(worker);
+               /*
+                * Only the worker continuation helper has worker allocated and
+                * hence needs freeing.
+                */
+               if (cb->func == create_worker_cont)
+                       kfree(worker);
        }
 }