netdev - [PATCH net-next] net: ipv4: fix rcu lockdep splat due to wrong annotation

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Message-Id: <20190603204144.28320-1-fw@strlen.de>
Date:   Mon,  3 Jun 2019 22:41:44 +0200
From:   Florian Westphal <fw@...len.de>
To:     <netdev@...r.kernel.org>
Cc:     syzbot+bad6e32808a3a97b1515@...kaller.appspotmail.com,
        Florian Westphal <fw@...len.de>
Subject: [PATCH net-next] net: ipv4: fix rcu lockdep splat due to wrong annotation

syzbot triggered following splat when strict netlink
validation is enabled:

net/ipv4/devinet.c:1766 suspicious rcu_dereference_check() usage!

This occurs because we hold RTNL mutex, but no rcu read lock.
The second call site holds both, so just switch to the _rtnl variant.

Reported-by: syzbot+bad6e32808a3a97b1515@...kaller.appspotmail.com
Fixes: 2638eb8b50cf ("net: ipv4: provide __rcu annotation for ifa_list")
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/ipv4/devinet.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index ebaea05b4033..ed2e2dc745cd 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1763,7 +1763,7 @@ static int in_dev_dump_addr(struct in_device *in_dev, struct sk_buff *skb,
 	int ip_idx = 0;
 	int err;
 
-	in_dev_for_each_ifa_rcu(ifa, in_dev) {
+	in_dev_for_each_ifa_rtnl(ifa, in_dev) {
 		if (ip_idx < s_ip_idx) {
 			ip_idx++;
 			continue;
-- 
2.21.0