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From:   Jamal Hadi Salim <jhs@mojatatu.com>
Date:   Sun, 25 Sep 2022 12:14:44 -0400
Message-ID: <CAM0EoMm9uBQQepMb5bda1vR-Okw-tPp2nnf6TvfA0FzPu_D_2A@mail.gmail.com>
Subject: Re: [syzbot] WARNING in u32_change
To:     syzbot <syzbot+a2c4601efc75848ba321@syzkaller.appspotmail.com>
Cc:     davem@davemloft.net, edumazet@google.com, jiri@resnulli.us,
        kuba@kernel.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, pabeni@redhat.com,
        syzkaller-bugs@googlegroups.com, xiyou.wangcong@gmail.com
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On Sun, Sep 25, 2022 at 11:38 AM Jamal Hadi Salim <jhs@mojatatu.com> wrote:
>
> Is there a way to tell the boat "looking into it?"


I guess I have to swim across to it to get the message;->

I couldnt see the warning message  but it is obvious by inspection that
the memcpy is broken. We should add more test coverage.
This should fix it. Will send a formal patch later:

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 4d27300c2..591cbbf27 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -1019,7 +1019,7 @@ static int u32_change(struct net *net, struct
sk_buff *in_skb,
        }

        s = nla_data(tb[TCA_U32_SEL]);
-       sel_size = struct_size(s, keys, s->nkeys);
+       sel_size = struct_size(s, keys, s->nkeys) + sizeof(n->sel);
        if (nla_len(tb[TCA_U32_SEL]) < sel_size) {
                err = -EINVAL;
                goto erridr;