From: Pavel Begunkov <asml.silence@xxxxxxxxx> commit bf68b5b34311ee57ed40749a1257a30b46127556 upstream. req->cqe.res is set in io_read() to the amount of bytes left to be done, which is used to figure out whether to fail a read or not. However, io_read() may do another without returning, and we stash the previous value into ->bytes_done but forget to update cqe.res. Then we ask a read to do strictly less than cqe.res but expect the return to be exactly cqe.res. Fix the bug by updating cqe.res for retries. Cc: stable@xxxxxxxxxxxxxxx Reported-and-Tested-by: Beld Zhang <beldzhang@xxxxxxxxx> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> Link: https://lore.kernel.org/r/3a1088440c7be98e5800267af922a67da0ef9f13.1664235732.git.asml.silence@xxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- io_uring/io_uring.c | 1 + 1 file changed, 1 insertion(+) --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -4215,6 +4215,7 @@ static int io_read(struct io_kiocb *req, return -EAGAIN; } + req->cqe.res = iov_iter_count(&s->iter); /* * Now retry read with the IOCB_WAITQ parts set in the iocb. If * we get -EIOCBQUEUED, then we'll get a notification when the
