rtnetlink: fix if_nlmsg_stats_size() under estimation

[ Upstream commit d34367991933d28bd7331f67a759be9a8c474014 ]

rtnl_fill_statsinfo() is filling skb with one mandatory if_stats_msg structure.

nlmsg_put(skb, pid, seq, type, sizeof(struct if_stats_msg), flags);

But if_nlmsg_stats_size() never considered the needed storage.

This bug did not show up because alloc_skb(X) allocates skb with
extra tailroom, because of added alignments. This could very well
be changed in the future to have deterministic behavior.

Fixes: 92d64bdc6015 ("rtnetlink: add new RTM_GETSTATS message to dump link stats")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Roopa Prabhu <roopa@nvidia.com>
Acked-by: Roopa Prabhu <roopa@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 6fbc9cb09dc0e6f3e4f001c93b8d54664d2119c5..a53b101ce41ae6470b793c0fce6e7b079f8fc69b 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -4950,7 +4950,7 @@ nla_put_failure:
 static size_t if_nlmsg_stats_size(const struct net_device *dev,
                                  u32 filter_mask)
 {
-       size_t size = 0;
+       size_t size = NLMSG_ALIGN(sizeof(struct if_stats_msg));
 
        if (stats_attr_valid(filter_mask, IFLA_STATS_LINK_64, 0))
                size += nla_total_size_64bit(sizeof(struct rtnl_link_stats64));