1 files changed, 62 insertions, 4 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 95931a5a9883..6daea0c91862 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -358,6 +358,66 @@ static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
         return mask;
 }
 
+/* prepad is the amount to reserve at front.  len is length after that.
+ * linear is a hint as to how much to copy (usually headers). */
+static struct sk_buff *tun_alloc_skb(size_t prepad, size_t len, size_t linear,
+                                     gfp_t gfp)
+{
+        struct sk_buff *skb;
+        unsigned int i;
+
+        skb = alloc_skb(prepad + len, gfp|__GFP_NOWARN);
+        if (skb) {
+                skb_reserve(skb, prepad);
+                skb_put(skb, len);
+                return skb;
+        }
+
+        /* Under a page?  Don't bother with paged skb. */
+        if (prepad + len < PAGE_SIZE)
+                return NULL;
+
+        /* Start with a normal skb, and add pages. */
+        skb = alloc_skb(prepad + linear, gfp);
+        if (!skb)
+                return NULL;
+
+        skb_reserve(skb, prepad);
+        skb_put(skb, linear);
+
+        len -= linear;
+
+        for (i = 0; i < MAX_SKB_FRAGS; i++) {
+                skb_frag_t *f = &skb_shinfo(skb)->frags[i];
+
+                f->page = alloc_page(gfp|__GFP_ZERO);
+                if (!f->page)
+                        break;
+
+                f->page_offset = 0;
+                f->size = PAGE_SIZE;
+
+                skb->data_len += PAGE_SIZE;
+                skb->len += PAGE_SIZE;
+                skb->truesize += PAGE_SIZE;
+                skb_shinfo(skb)->nr_frags++;
+
+                if (len < PAGE_SIZE) {
+                        len = 0;
+                        break;
+                }
+                len -= PAGE_SIZE;
+        }
+
+        /* Too large, or alloc fail? */
+        if (unlikely(len)) {
+                kfree_skb(skb);
+                skb = NULL;
+        }
+
+        return skb;
+}
+
 /* Get packet from user space buffer */
 static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv, size_t count)
 {
@@ -391,14 +451,12 @@ static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv,
                         return -EINVAL;
         }
 
-        if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
+        if (!(skb = tun_alloc_skb(align, len, gso.hdr_len, GFP_KERNEL))) {
                 tun->dev->stats.rx_dropped++;
                 return -ENOMEM;
         }
 
-        if (align)
-                skb_reserve(skb, align);
-        if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
+        if (skb_copy_datagram_from_iovec(skb, 0, iv, len)) {
                 tun->dev->stats.rx_dropped++;
                 kfree_skb(skb);
                 return -EFAULT;