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[209.85.222.44]) by smtp.gmail.com with ESMTPSA id v76sm861512vke.2.2020.10.08.13.19.45 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 08 Oct 2020 13:19:45 -0700 (PDT) Received: by mail-ua1-f44.google.com with SMTP id d18so2313187uae.0 for ; Thu, 08 Oct 2020 13:19:45 -0700 (PDT) X-Received: by 2002:ab0:6495:: with SMTP id p21mr5972181uam.108.1602188385086; Thu, 08 Oct 2020 13:19:45 -0700 (PDT) MIME-Version: 1.0 References: <20201008012154.11149-1-xiyou.wangcong@gmail.com> In-Reply-To: <20201008012154.11149-1-xiyou.wangcong@gmail.com> From: Willem de Bruijn Date: Thu, 8 Oct 2020 16:19:10 -0400 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [Patch net] ip_gre: set dev->hard_header_len properly To: Cong Wang Cc: Network Development , syzbot , William Tu , Willem de Bruijn Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Oct 7, 2020 at 9:22 PM Cong Wang wrote: > > GRE tunnel has its own header_ops, ipgre_header_ops, and sets it > conditionally. When it is set, it assumes the outer IP header is > already created before ipgre_xmit(). > > This is not true when we send packets through a raw packet socket, > where L2 headers are supposed to be constructed by user. Packet > socket calls dev_validate_header() to validate the header. But > GRE tunnel does not set dev->hard_header_len, so that check can > be simply bypassed, therefore uninit memory could be passed down > to ipgre_xmit(). > > Fix this by setting dev->hard_header_len whenever sets header_ops, > as dev->hard_header_len is supposed to be the length of the header > created by dev->header_ops->create() anyway. > > Reported-and-tested-by: syzbot+4a2c52677a8a1aa283cb@syzkaller.appspotmail.com > Cc: William Tu > Cc: Willem de Bruijn > Signed-off-by: Cong Wang Acked-by: Willem de Bruijn > The syzbot report has the information for both of your questions: > https://syzkaller.appspot.com/text?tag=CrashReport&x=11845568500000 > > It clearly shows packet_snd() and ipgre_xmit(). Thanks. I hadn't thought to check that (clearly).