Commit d4e7cd36 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: sanitize double poll handling 



There's a bit of confusion on the matching pairs of poll vs double poll,
depending on if the request is a pure poll (IORING_OP_POLL_ADD) or
poll driven retry.

Add io_poll_get_double() that returns the double poll waitqueue, if any,
and io_poll_get_single() that returns the original poll waitqueue. With
that, remove the argument to io_poll_remove_double().

Finally ensure that wait->private is cleared once the double poll handler
has run, so that remove knows it's already been seen.

Cc: stable@vger.kernel.org # v5.8
Reported-by: default avatar <syzbot+7f617d4a9369028b8a2c@syzkaller.appspotmail.com>
Fixes: 18bceab1 ("io_uring: allow POLL_ADD with double poll_wait() users")
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 227c0c96

fs/io_uring.c

+25 −9
Original line number Diff line number Diff line
@@ -4649,9 +4649,24 @@ static bool io_poll_rewait(struct io_kiocb *req, struct io_poll_iocb *poll) 
	return false;

}



static void io_poll_remove_double(struct io_kiocb *req, void *data)

static struct io_poll_iocb *io_poll_get_double(struct io_kiocb *req)

{

	struct io_poll_iocb *poll = data;

	/* pure poll stashes this in ->io, poll driven retry elsewhere */

	if (req->opcode == IORING_OP_POLL_ADD)

		return (struct io_poll_iocb *) req->io;

	return req->apoll->double_poll;

}



static struct io_poll_iocb *io_poll_get_single(struct io_kiocb *req)

{

	if (req->opcode == IORING_OP_POLL_ADD)

		return &req->poll;

	return &req->apoll->poll;

}



static void io_poll_remove_double(struct io_kiocb *req)

{

	struct io_poll_iocb *poll = io_poll_get_double(req);



	lockdep_assert_held(&req->ctx->completion_lock);
@@ -4671,7 +4686,7 @@ static void io_poll_complete(struct io_kiocb *req, __poll_t mask, int error) 
{

	struct io_ring_ctx *ctx = req->ctx;



	io_poll_remove_double(req, req->io);

	io_poll_remove_double(req);

	req->poll.done = true;

	io_cqring_fill_event(req, error ? error : mangle_poll(mask));

	io_commit_cqring(ctx);
@@ -4711,7 +4726,7 @@ static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode, 
			       int sync, void *key)

{

	struct io_kiocb *req = wait->private;

	struct io_poll_iocb *poll = req->apoll->double_poll;

	struct io_poll_iocb *poll = io_poll_get_single(req);

	__poll_t mask = key_to_poll(key);



	/* for instances that support it check for an event match first: */
@@ -4725,6 +4740,8 @@ static int io_poll_double_wake(struct wait_queue_entry *wait, unsigned mode, 
		done = list_empty(&poll->wait.entry);

		if (!done)

			list_del_init(&poll->wait.entry);

		/* make sure double remove sees this as being gone */

		wait->private = NULL;

		spin_unlock(&poll->head->lock);

		if (!done)

			__io_async_wake(req, poll, mask, io_poll_task_func);
@@ -4808,7 +4825,7 @@ static void io_async_task_func(struct callback_head *cb) 
	if (hash_hashed(&req->hash_node))

		hash_del(&req->hash_node);



	io_poll_remove_double(req, apoll->double_poll);

	io_poll_remove_double(req);

	spin_unlock_irq(&ctx->completion_lock);



	if (!READ_ONCE(apoll->poll.canceled))
@@ -4919,7 +4936,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req) 
	ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask,

					io_async_wake);

	if (ret || ipt.error) {

		io_poll_remove_double(req, apoll->double_poll);

		io_poll_remove_double(req);

		spin_unlock_irq(&ctx->completion_lock);

		kfree(apoll->double_poll);

		kfree(apoll);
@@ -4951,14 +4968,13 @@ static bool io_poll_remove_one(struct io_kiocb *req) 
{

	bool do_complete;



	io_poll_remove_double(req);



	if (req->opcode == IORING_OP_POLL_ADD) {

		io_poll_remove_double(req, req->io);

		do_complete = __io_poll_remove_one(req, &req->poll);

	} else {

		struct async_poll *apoll = req->apoll;



		io_poll_remove_double(req, apoll->double_poll);



		/* non-poll requests have submit ref still */

		do_complete = __io_poll_remove_one(req, &apoll->poll);

		if (do_complete) {

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