io_uring: io_wq_submit_work() should not touch req->rw

I've been chasing a weird and obscure crash that was userspace stack
corruption, and finally narrowed it down to a bit flip that made a
stack address invalid. io_wq_submit_work() unconditionally flips
the req->rw.ki_flags IOCB_NOWAIT bit, but since it's a generic work
handler, this isn't valid. Normal read/write operations own that
part of the request, on other types it could be something else.

Move the IOCB_NOWAIT clear to the read/write handlers where it belongs.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 81e7fe6..6f084e3 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1817,6 +1817,10 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
                        return ret;
        }
 
+       /* Ensure we clear previously set non-block flag */
+       if (!force_nonblock)
+               req->rw.ki_flags &= ~IOCB_NOWAIT;
+
        file = req->file;
        io_size = ret;
        if (req->flags & REQ_F_LINK)
@@ -1906,6 +1910,10 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
                        return ret;
        }
 
+       /* Ensure we clear previously set non-block flag */
+       if (!force_nonblock)
+               req->rw.ki_flags &= ~IOCB_NOWAIT;
+
        file = kiocb->ki_filp;
        io_size = ret;
        if (req->flags & REQ_F_LINK)
@@ -3274,9 +3282,6 @@ static void io_wq_submit_work(struct io_wq_work **workptr)
        struct io_kiocb *nxt = NULL;
        int ret = 0;
 
-       /* Ensure we clear previously set non-block flag */
-       req->rw.ki_flags &= ~IOCB_NOWAIT;
-
        if (work->flags & IO_WQ_WORK_CANCEL)
                ret = -ECANCELED;