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From:   Fedor Pchelkin <pchelkin@ispras.ru>
To:     stable@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Fedor Pchelkin <pchelkin@ispras.ru>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Sasha Levin <sashal@kernel.org>,
        Nicolas Dichtel <nicolas.dichtel@6wind.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Alexey Khoroshilov <khoroshilov@ispras.ru>,
        lvc-project@linuxtesting.org,
        syzbot+3d9866419b4aa8f985d6@syzkaller.appspotmail.com
Subject: [PATCH 5.10 1/1] xfrm: fix rcu lock in xfrm_notify_userpolicy()
Date:   Sat, 14 Jan 2023 23:58:49 +0300
Message-Id: <20230114205850.176370-2-pchelkin@ispras.ru>
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From: Nicolas Dichtel <nicolas.dichtel@6wind.com>

commit 93ec1320b0170d7a207eda2d119c669b673401ed upstream.

As stated in the comment above xfrm_nlmsg_multicast(), rcu read lock must
be held before calling this function.

Reported-by: syzbot+3d9866419b4aa8f985d6@syzkaller.appspotmail.com
Fixes: 9856c3a129dd ("xfrm: notify default policy on update")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
---
 net/xfrm/xfrm_user.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index d9841f44487f..b5a517916895 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1920,6 +1920,7 @@ static int xfrm_notify_userpolicy(struct net *net)
 	int len = NLMSG_ALIGN(sizeof(*up));
 	struct nlmsghdr *nlh;
 	struct sk_buff *skb;
+	int err;
 
 	skb = nlmsg_new(len, GFP_ATOMIC);
 	if (skb == NULL)
@@ -1938,7 +1939,10 @@ static int xfrm_notify_userpolicy(struct net *net)
 
 	nlmsg_end(skb, nlh);
 
-	return xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY);
+	rcu_read_lock();
+	err = xfrm_nlmsg_multicast(net, skb, 0, XFRMNLGRP_POLICY);
+	rcu_read_unlock();
+	return err;
 }
 
 static bool xfrm_userpolicy_is_valid(__u8 policy)
-- 
2.34.1