io_uring: don't run task work on an exiting task

This isn't safe, and isn't needed either. We are guaranteed that any
work we queue is on a live task (and will be run), or it goes to
our backup io-wq threads if the task is exiting.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 01756a1..a29c891 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1753,6 +1753,9 @@ static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb,
        struct io_ring_ctx *ctx = req->ctx;
        int ret, notify;
 
+       if (tsk->flags & PF_EXITING)
+               return -ESRCH;
+
        /*
         * SQPOLL kernel thread doesn't need notification, just a wakeup. For
         * all other cases, use TWA_SIGNAL unconditionally to ensure we're
@@ -2012,6 +2015,12 @@ static inline unsigned int io_put_rw_kbuf(struct io_kiocb *req)
 
 static inline bool io_run_task_work(void)
 {
+       /*
+        * Not safe to run on exiting task, and the task_work handling will
+        * not add work to such a task.
+        */
+       if (unlikely(current->flags & PF_EXITING))
+               return false;
        if (current->task_works) {
                __set_current_state(TASK_RUNNING);
                task_work_run();
@@ -8184,6 +8193,8 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
                /* cancel this request, or head link requests */
                io_attempt_cancel(ctx, cancel_req);
                io_put_req(cancel_req);
+               /* cancellations _may_ trigger task work */
+               io_run_task_work();
                schedule();
                finish_wait(&ctx->inflight_wait, &wait);
        }