netdev - [PATCH v2] netlink: fixup regression in RTM

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Date:   Mon, 31 Dec 2018 02:10:58 +0000
From:   baloo@...di.net
To:     netdev@...r.kernel.org
Cc:     Arthur Gautier <baloo@...di.net>, David Ahern <dsahern@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: [PATCH v2] netlink: fixup regression in RTM_GETADDR

From: Arthur Gautier <baloo@...di.net>

This commit fixes a regression in AF_INET/RTM_GETADDR and
AF_INET6/RTM_GETADDR.

Before this commit, the kernel would stop dumping addresses once the first
skb was full and end the stream with NLMSG_DONE(-EMSGSIZE). The error
shouldn't be sent back to netlink_dump so the callback is kept alive. The
userspace is expected to call back with a new empty skb.

Changes from V1:
 - The error is not handled in netlink_dump anymore but rather in
   inet_dump_ifaddr and inet6_dump_addr directly as suggested by
   David Ahern.

Fixes: d7e38611b81e ("net/ipv4: Put target net when address dump fails due to bad attributes")
Fixes: 242afaa6968c ("net/ipv6: Put target net when address dump fails due to bad attributes")

Cc: David Ahern <dsahern@...il.com>
Cc: "David S . Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Signed-off-by: Arthur Gautier <baloo@...di.net>
---
 net/ipv4/devinet.c  | 2 +-
 net/ipv6/addrconf.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 608a6f4223fb9..fecd0e7672b5d 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1826,7 +1826,7 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
 	if (fillargs.netnsid >= 0)
 		put_net(tgt_net);
 
-	return err < 0 ? err : skb->len;
+	return skb->len ? : err;
 }
 
 static void rtmsg_ifa(int event, struct in_ifaddr *ifa, struct nlmsghdr *nlh,
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 045597b9a7c05..e3cb53b0ef670 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5154,7 +5154,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 	if (fillargs.netnsid >= 0)
 		put_net(tgt_net);
 
-	return err < 0 ? err : skb->len;
+	return skb->len ? : err;
 }
 
 static int inet6_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
-- 
2.20.1