io_uring/rw: forbid multishot async reads

At the moment we can't sanely handle queuing an async request from a
multishot context, so disable them. It shouldn't matter as pollable
files / socekts don't normally do async.

Patching it in __io_read() is not the cleanest way, but it's simpler
than other options, so let's fix it there and clean up on top.

Cc: stable@vger.kernel.org
Reported-by: chase xd <sl1589472800@gmail.com>
Fixes: fc68fcda04910 ("io_uring/rw: add support for IORING_OP_READ_MULTISHOT")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/7d51732c125159d17db4fe16f51ec41b936973f8.1739919038.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/rw.c b/io_uring/rw.c
index 7aa1e4c9f64a31753ed4ce29ef873aff39804086..e8efd97fdee5ba62a8dc99586edef970df8965b4 100644 (file)
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -880,7 +880,15 @@ static int __io_read(struct io_kiocb *req, unsigned int issue_flags)
        if (unlikely(ret))
                return ret;
 
-       ret = io_iter_do_read(rw, &io->iter);
+       if (unlikely(req->opcode == IORING_OP_READ_MULTISHOT)) {
+               void *cb_copy = rw->kiocb.ki_complete;
+
+               rw->kiocb.ki_complete = NULL;
+               ret = io_iter_do_read(rw, &io->iter);
+               rw->kiocb.ki_complete = cb_copy;
+       } else {
+               ret = io_iter_do_read(rw, &io->iter);
+       }
 
        /*
         * Some file systems like to return -EOPNOTSUPP for an IOCB_NOWAIT
@@ -904,7 +912,8 @@ static int __io_read(struct io_kiocb *req, unsigned int issue_flags)
        } else if (ret == -EIOCBQUEUED) {
                return IOU_ISSUE_SKIP_COMPLETE;
        } else if (ret == req->cqe.res || ret <= 0 || !force_nonblock ||
-                  (req->flags & REQ_F_NOWAIT) || !need_complete_io(req)) {
+                  (req->flags & REQ_F_NOWAIT) || !need_complete_io(req) ||
+                  (issue_flags & IO_URING_F_MULTISHOT)) {
                /* read all, failed, already did sync or don't want to retry */
                goto done;
        }