tun: fix tun_chr_aio_write so that aio works

aio_write gets const struct iovec * but tun_chr_aio_write casts this to struct
iovec * and modifies the iovec. As a result, attempts to use io_submit
to send packets to a tun device fail with weird errors such as EINVAL.

Since tun is the only user of skb_copy_datagram_from_iovec, we can
fix this simply by changing the later so that it does not
touch the iovec passed to it.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/core/iovec.c b/net/core/iovec.c
index a215545c0a34..40a76ce19d9f 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -147,10 +147,11 @@ int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
 }
 
 /*
- *      For use with ip_build_xmit
+ *      Copy iovec from kernel. Returns -EFAULT on error.
  */
-int memcpy_fromiovecend(unsigned char *kdata, struct iovec *iov, int offset,
-                        int len)
+
+int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
+                        int offset, int len)
 {
         /* Skip over the finished iovecs */
         while (offset >= iov->iov_len) {