linux-kernel - [PATCH 4.9 17/25] rtnetlink: fix if_nlmsg_stats

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Message-Id: <20211014145208.123950311@linuxfoundation.org>
Date:   Thu, 14 Oct 2021 16:53:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        Roopa Prabhu <roopa@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 17/25] rtnetlink: fix if_nlmsg_stats_size() under estimation

From: Eric Dumazet <edumazet@...gle.com>

[ 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: 10c9ead9f3c6 ("rtnetlink: add new RTM_GETSTATS message to dump link stats")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Roopa Prabhu <roopa@...dia.com>
Acked-by: Roopa Prabhu <roopa@...dia.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/core/rtnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 911752e8a3e6..012143f313a8 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3900,7 +3900,7 @@ 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));
-- 
2.33.0