linux-kernel - Re: WARNING in __rcu_read

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Message-ID: <20181217162421.6d636ee5@redhat.com>
Date:   Mon, 17 Dec 2018 16:24:21 +0100
From:   Stefano Brivio <sbrivio@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        syzbot <syzbot+43f6755d1c2e62743468@...kaller.appspotmail.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Josh Triplett <josh@...htriplett.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: WARNING in __rcu_read_unlock

On Mon, 17 Dec 2018 06:57:35 -0800
Eric Dumazet <eric.dumazet@...il.com> wrote:

> Might be cause by commit b8a51b38e4d4dec3e379d52c0fe1a66827f7cf1e
> fou, fou6: ICMP error handlers for FoU and GUE

This:

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 0d0ad19ecb87..20a6de26d146 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -1008,6 +1008,9 @@ static int gue_err_proto_handler(int proto, struct sk_buff *skb, u32 info)
 {
        const struct net_protocol *ipprot = rcu_dereference(inet_protos[proto]);
 
+       if (ipprot == IPPROTO_UDP)
+               return -EINVAL;
+
        if (ipprot && ipprot->err_handler) {
                if (!ipprot->err_handler(skb, info))
                        return 0;

should fix the issue, but I still have to run tests and make sure we
don't hit similar cases.

-- 
Stefano