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, 8 insertions, 5 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3b513e29d392..589f0ca668d6 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -540,31 +540,34 @@ static inline struct sk_buff *tun_alloc_skb(struct tun_struct *tun,
 
 /* Get packet from user space buffer */
 static __inline__ ssize_t tun_get_user(struct tun_struct *tun,
-                                       struct iovec *iv, size_t count,
+                                       const struct iovec *iv, size_t count,
                                        int noblock)
 {
         struct tun_pi pi = { 0, cpu_to_be16(ETH_P_IP) };
         struct sk_buff *skb;
         size_t len = count, align = 0;
         struct virtio_net_hdr gso = { 0 };
+        int offset = 0;
 
         if (!(tun->flags & TUN_NO_PI)) {
                 if ((len -= sizeof(pi)) > count)
                         return -EINVAL;
 
-                if(memcpy_fromiovec((void *)&pi, iv, sizeof(pi)))
+                if (memcpy_fromiovecend((void *)&pi, iv, 0, sizeof(pi)))
                         return -EFAULT;
+                offset += sizeof(pi);
         }
 
         if (tun->flags & TUN_VNET_HDR) {
                 if ((len -= sizeof(gso)) > count)
                         return -EINVAL;
 
-                if (memcpy_fromiovec((void *)&gso, iv, sizeof(gso)))
+                if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))
                         return -EFAULT;
 
                 if (gso.hdr_len > len)
                         return -EINVAL;
+                offset += sizeof(pi);
         }
 
         if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
@@ -581,7 +584,7 @@ static __inline__ ssize_t tun_get_user(struct tun_struct *tun,
                 return PTR_ERR(skb);
         }
 
-        if (skb_copy_datagram_from_iovec(skb, 0, iv, len)) {
+        if (skb_copy_datagram_from_iovec(skb, 0, iv, offset, len)) {
                 tun->dev->stats.rx_dropped++;
                 kfree_skb(skb);
                 return -EFAULT;
@@ -673,7 +676,7 @@ static ssize_t tun_chr_aio_write(struct kiocb *iocb, const struct iovec *iv,
 
         DBG(KERN_INFO "%s: tun_chr_write %ld\n", tun->dev->name, count);
 
-        result = tun_get_user(tun, (struct iovec *)iv, iov_length(iv, count),
+        result = tun_get_user(tun, iv, iov_length(iv, count),
                               file->f_flags & O_NONBLOCK);
 
         tun_put(tun);