io_uring: don't map read/write iovec potentially twice

If we have a read/write that is deferred, we already setup the async IO
context for that request, and mapped it. When we later try and execute
the request and we get -EAGAIN, we don't want to attempt to re-map it.
If we do, we end up with garbage in the iovec, which typically leads
to an -EFAULT or -EINVAL completion.

Cc: stable@vger.kernel.org # 5.5
Reported-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cd07df2..678a1b2 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2171,10 +2171,12 @@ static int io_setup_async_rw(struct io_kiocb *req, ssize_t io_size,
 {
        if (!io_op_defs[req->opcode].async_ctx)
                return 0;
-       if (!req->io && io_alloc_async_ctx(req))
-               return -ENOMEM;
+       if (!req->io) {
+               if (io_alloc_async_ctx(req))
+                       return -ENOMEM;
 
-       io_req_map_rw(req, io_size, iovec, fast_iov, iter);
+               io_req_map_rw(req, io_size, iovec, fast_iov, iter);
+       }
        req->work.func = io_rw_async;
        return 0;
 }