net: Fix unwanted sign extension in netdev_stats_to_stats64()

When converting net_device_stats to rtnl_link_stats64 sign extension
is triggered on ILP32 machines as 6c1c509778 changed the previous
"ulong -> u64" conversion to "long -> u64" by accessing the
net_device_stats fields through a (signed) atomic_long_t.

This causes for example the received bytes counter to jump to 16EiB after
having received 2^31 bytes. Casting the atomic value to "unsigned long"
beforehand converting it into u64 avoids this.

Fixes: 6c1c5097781f ("net: add atomic_long_t to net_device_stats fields")
Signed-off-by: Felix Riemann <felix.riemann@sma.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index b76fb37b381e96af8d52dbadca163202eb4f3ccb..ea0a7bac1e5c3602b1158c330ef39543c8e6e6d3 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10375,7 +10375,7 @@ void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
 
        BUILD_BUG_ON(n > sizeof(*stats64) / sizeof(u64));
        for (i = 0; i < n; i++)
-               dst[i] = atomic_long_read(&src[i]);
+               dst[i] = (unsigned long)atomic_long_read(&src[i]);
        /* zero out counters that only exist in rtnl_link_stats64 */
        memset((char *)stats64 + n * sizeof(u64), 0,
               sizeof(*stats64) - n * sizeof(u64));