net: prevent sign extension in dev_get_stats()

commit 6f64ec74515925cced6df4571638b5a099a49aae upstream.

Similar to the fix provided by Dominik Heidler in commit
9b3dc0a17d73 ("l2tp: cast l2tp traffic counter to unsigned")
we need to take care of 32bit kernels in dev_get_stats().

When using atomic_long_read(), we add a 'long' to u64 and
might misinterpret high order bit, unless we cast to unsigned.

Fixes: caf586e5f23ce ("net: add a core netdev->rx_dropped counter")
Fixes: 015f0688f57ca ("net: net: add a core netdev->tx_dropped counter")
Fixes: 6e7333d315a76 ("net: add rx_nohandler stat counter")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jarod Wilson <jarod@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2: only rx_dropped is updated here]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/core/dev.c b/net/core/dev.c
index 164958d..bb7a0cc 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5942,7 +5942,7 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
        } else {
                netdev_stats_to_stats64(storage, &dev->stats);
        }
-       storage->rx_dropped += atomic_long_read(&dev->rx_dropped);
+       storage->rx_dropped += (unsigned long)atomic_long_read(&dev->rx_dropped);
        return storage;
 }
 EXPORT_SYMBOL(dev_get_stats);