ppp_generic: handle non-linear skbs when passing them to pppd

Frequently when using PPPoE with an interface MTU greater than 1500,
the skb is likely to be non-linear. If the skb needs to be passed to
pppd then the skb data must be read correctly.

The previous commit fixes an issue with accidentally sending skbs
to pppd based on an invalid read of the protocol type. When that
error occurred pppd was reading invalid skb data too.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/net/ppp_generic.c b/drivers/net/ppp_generic.c
index 75e8903c3754..8518a2e58e53 100644
--- a/drivers/net/ppp_generic.c
+++ b/drivers/net/ppp_generic.c
@@ -405,6 +405,7 @@ static ssize_t ppp_read(struct file *file, char __user *buf,
         DECLARE_WAITQUEUE(wait, current);
         ssize_t ret;
         struct sk_buff *skb = NULL;
+        struct iovec iov;
 
         ret = count;
 
@@ -448,7 +449,9 @@ static ssize_t ppp_read(struct file *file, char __user *buf,
         if (skb->len > count)
                 goto outf;
         ret = -EFAULT;
-        if (copy_to_user(buf, skb->data, skb->len))
+        iov.iov_base = buf;
+        iov.iov_len = count;
+        if (skb_copy_datagram_iovec(skb, 0, &iov, skb->len))
                 goto outf;
         ret = skb->len;