From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-vs1-f44.google.com (mail-vs1-f44.google.com [209.85.217.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 198C115B0 for ; Fri, 23 Sep 2022 02:23:50 +0000 (UTC) Received: by mail-vs1-f44.google.com with SMTP id k2so12277203vsk.8 for ; Thu, 22 Sep 2022 19:23:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date; bh=j+mjDeU8MfTaoo2Hr5w1v30IzbKSmgNAkOvuWkOsXjM=; b=UMtVs9r6osj9VmxhbEMYKQzKkleV/r446iRFxqMvE/gbFQVZaizc6S8gprSj6kO3Ds N+tt8rVMwKl908yhk9ENaHYDZZSYDiFaqmj/oMNdQYMXghvmG6DGfX4e+R5gUxKTwvMw Y0JY9godWbtlKhD/4bTK+2r62kwutzBOxT5BNEqeZvaa8hcJe3skwHqWrmVkKUMTX6Bf hHCJaYzcw/ca9h4kv/jUsV3gN9RjZn9CTwv/aOz+6L3ON3GlD14zztk9oXwVS1AyZPXm QrIHjrASqemJU9GOjRaJIhDwfzbgTtC5yufuzo1lEOfkvLexyEhhf8ECO1SOlJBAdGGS CT6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date; bh=j+mjDeU8MfTaoo2Hr5w1v30IzbKSmgNAkOvuWkOsXjM=; b=4cehkA2tSNVr3W2KygfYhfAF7o5GXT6T2wxHlxrKbwJmh9UXkjrWd5wQQBMrrq4uBS fSPjK8ldiJTnNHV1QXF9v7d/TccY0haksZ0Fy8/n9NMoAmkBwyvwYNSyZMDMDlbbNZVt kpzPl3MONiUzAG7vi0brakbbsj46VnoMTHAva4BXSSiZytWHJvW7do7P7dlPo8ie/gHH P4lf/K7swybIzgb+cIt8MW3pn05zYaM+fTtKTK0qsfm9o8aWBSGohNa82vSUMVCcrt+7 K1nY6aG/E/knBAu6Nxf4AyIo1jhBDJrCw2ZtSV5PDaG4iM6qrHmbd6wi0SsTuyyPy/BY v7bg== X-Gm-Message-State: ACrzQf0B+YmLXSA24GFzQcMa+hqZ7vz3CU+haZqbAREAJGa2NM1Q0MTS uTmlQq5V8zej+H2ozgWtw5JiRiIgfzNy3J9VKjU= X-Google-Smtp-Source: AMsMyM4RqEWUTYLvpo5uDoNc12YKavzt8E+kH8ArJyRF2vgLlGG6O1oGmDR2maiMAwQbZCIvRZ2jJTrYcNSe1MdMMU8= X-Received: by 2002:a67:e401:0:b0:398:89f1:492f with SMTP id d1-20020a67e401000000b0039889f1492fmr2891816vsf.21.1663899829770; Thu, 22 Sep 2022 19:23:49 -0700 (PDT) Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <48ba286b429284accc457e34c6580efcdec593c4.1662725968.git.geliang.tang@suse.com> <99b1363eeecf160159bbe9f37e38221e93baef55.camel@redhat.com> In-Reply-To: <99b1363eeecf160159bbe9f37e38221e93baef55.camel@redhat.com> From: Geliang Tang Date: Fri, 23 Sep 2022 10:24:26 +0800 Message-ID: Subject: Re: [PATCH mptcp-next] tcp: Add mss zero checks to avoid divide errors To: Paolo Abeni Cc: Geliang Tang , mptcp@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Paolo, Sorry for the late reply. Paolo Abeni =E4=BA=8E2022=E5=B9=B49=E6=9C=889=E6=97=A5= =E5=91=A8=E4=BA=94 22:44=E5=86=99=E9=81=93=EF=BC=9A > > On Fri, 2022-09-09 at 20:19 +0800, Geliang Tang wrote: > > If mss_now is set to zero when invoking tcp_push(), this divide error w= ill occur: > > We should not call at all tcp_push() in such situation. How did you > reproduce the issue? This does not happen on the export branch, but only when I add the BPF redundant scheduler. > > Adding more check in TCP for the above situation is very likely not the > correct thing to do. Instead we should prevent MPTCP from reaching for > tcp_push() in the critical situation. I agree. Let's just drop this patch. I'll add the new one to avoid calling tcp_push() in such situation into the " BPF redundant scheduler" series If we really need it. Thanks! -Geliang > > Thanks! > > Paolo > >