Commit b7db41c9 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: fix regression with always ignoring signals in io_cqring_wait() 



When switching to TWA_SIGNAL for task_work notifications, we also made
any signal based condition in io_cqring_wait() return -ERESTARTSYS.
This breaks applications that rely on using signals to abort someone
waiting for events.

Check if we have a signal pending because of queued task_work, and
repeat the signal check once we've run the task_work. This provides a
reliable way of telling the two apart.

Additionally, only use TWA_SIGNAL if we are using an eventfd. If not,
we don't have the dependency situation described in the original commit,
and we can get by with just using TWA_RESUME like we previously did.

Fixes: ce593a6c ("io_uring: use signal based task_work running")
Cc: stable@vger.kernel.org # v5.7
Reported-by: default avatarAndres Freund <andres@anarazel.de>
Tested-by: default avatarAndres Freund <andres@anarazel.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent ce593a6c

fs/io_uring.c

+22 −7
Original line number Diff line number Diff line
@@ -4072,14 +4072,22 @@ struct io_poll_table { 
	int error;

};



static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb,

				int notify)

static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb)

{

	struct task_struct *tsk = req->task;

	int ret;

	struct io_ring_ctx *ctx = req->ctx;

	int ret, notify = TWA_RESUME;



	if (req->ctx->flags & IORING_SETUP_SQPOLL)

	/*

	 * SQPOLL kernel thread doesn't need notification, just a wakeup.

	 * If we're not using an eventfd, then TWA_RESUME is always fine,

	 * as we won't have dependencies between request completions for

	 * other kernel wait conditions.

	 */

	if (ctx->flags & IORING_SETUP_SQPOLL)

		notify = 0;

	else if (ctx->cq_ev_fd)

		notify = TWA_SIGNAL;



	ret = task_work_add(tsk, cb, notify);

	if (!ret)
@@ -4110,7 +4118,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll, 
	 * of executing it. We can't safely execute it anyway, as we may not

	 * have the needed state needed for it anyway.

	 */

	ret = io_req_task_work_add(req, &req->task_work, TWA_SIGNAL);

	ret = io_req_task_work_add(req, &req->task_work);

	if (unlikely(ret)) {

		WRITE_ONCE(poll->canceled, true);

		tsk = io_wq_get_task(req->ctx->io_wq);
@@ -6201,7 +6209,14 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, 
		if (current->task_works)

			task_work_run();

		if (signal_pending(current)) {

			ret = -ERESTARTSYS;

			if (current->jobctl & JOBCTL_TASK_WORK) {

				spin_lock_irq(&current->sighand->siglock);

				current->jobctl &= ~JOBCTL_TASK_WORK;

				recalc_sigpending();

				spin_unlock_irq(&current->sighand->siglock);

				continue;

			}

			ret = -EINTR;

			break;

		}

		if (io_should_wake(&iowq, false))
@@ -6210,7 +6225,7 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, 
	} while (1);

	finish_wait(&ctx->wait, &iowq.wq);



	restore_saved_sigmask_unless(ret == -ERESTARTSYS);

	restore_saved_sigmask_unless(ret == -EINTR);



	return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE