io_uring: fix recvmsg setup with compat buf-select

commit 2d280bc8930ba9ed1705cfd548c6c8924949eaf1 upstream.

__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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6d729a278535e024d4134d7ba57383824a1a0eec..9f18c18ec8117906b295cf82c0608ca583db5417 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4300,7 +4300,8 @@ 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 = compat_import_iovec(READ, uiov, len, UIO_FASTIOV,