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>

2 files changed, 4 insertions, 3 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index af2b21bdda83..1b5c3d298f43 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1715,7 +1715,8 @@ extern int	       skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
                                                         struct iovec *iov);
 extern int             skb_copy_datagram_from_iovec(struct sk_buff *skb,
                                                     int offset,
-                                                    struct iovec *from,
+                                                    const struct iovec *from,
+                                                    int from_offset,
                                                     int len);
 extern int             skb_copy_datagram_const_iovec(const struct sk_buff *from,
                                                      int offset,
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 171b08db9c4f..42a0396f2c59 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -309,8 +309,8 @@ struct ucred {
 
 #ifdef __KERNEL__
 extern int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
-extern int memcpy_fromiovecend(unsigned char *kdata, struct iovec *iov, 
-                                int offset, int len);
+extern int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
+                               int offset, int len);
 extern int csum_partial_copy_fromiovecend(unsigned char *kdata, 
                                           struct iovec *iov, 
                                           int offset,