io_uring: fix recvmsg setup with compat buf-select

__io_compat_recvmsg_copy_hdr() with REQ_F_BUFFER_SELECT reads out iov
len but never assigns it to iov/fast_iov, leaving sr->len with garbage.
Hopefully, following io_buffer_select() truncates it to the selected
buffer size, but the value is still may be under what was specified.

Cc: <stable@vger.kernel.org> # 5.7
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1023f7b..a2a7c65 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4499,7 +4499,8 @@ static int __io_compat_recvmsg_copy_hdr(struct io_kiocb *req,
                        return -EFAULT;
                if (clen < 0)
                        return -EINVAL;
-               sr->len = iomsg->iov[0].iov_len;
+               sr->len = clen;
+               iomsg->iov[0].iov_len = clen;
                iomsg->iov = NULL;
        } else {
                ret = __import_iovec(READ, (struct iovec __user *)uiov, len,