From: Jens Axboe axboe@kernel.dk
commit d4e7cd36a90e38e0276d6ce0c20f5ccef17ec38c upstream.
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: syzbot+7f617d4a9369028b8a2c@syzkaller.appspotmail.com Fixes: 18bceab101ad ("io_uring: allow POLL_ADD with double poll_wait() users") Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/io_uring.c | 34 +++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4172,9 +4172,24 @@ static bool io_poll_rewait(struct io_kio 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);
@@ -4194,7 +4209,7 @@ static void io_poll_complete(struct io_k { 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); @@ -4236,7 +4251,7 @@ static int io_poll_double_wake(struct wa 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: */ @@ -4250,6 +4265,8 @@ static int io_poll_double_wake(struct wa 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); @@ -4358,7 +4375,7 @@ static void io_async_task_func(struct ca } }
- io_poll_remove_double(req, apoll->double_poll); + io_poll_remove_double(req); spin_unlock_irq(&ctx->completion_lock);
/* restore ->work in case we need to retry again */ @@ -4484,7 +4501,7 @@ static bool io_arm_poll_handler(struct i 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); if (req->flags & REQ_F_WORK_INITIALIZED) memcpy(&req->work, &apoll->work, sizeof(req->work)); @@ -4518,14 +4535,13 @@ static bool io_poll_remove_one(struct io { 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) {