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[88.21.205.111]) by smtp.gmail.com with ESMTPSA id a9sm25942094wrp.21.2020.11.30.02.44.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Nov 2020 02:44:17 -0800 (PST) Subject: Re: [PATCH] hw/net/dp8393x: fix integer underflow in dp8393x_do_transmit_packets() To: Mauro Matteo Cascella , qemu-devel@nongnu.org References: <20201124092445.658647-1-mcascell@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <48d8ae85-3292-921a-f249-3b88a1141cc9@amsat.org> Date: Mon, 30 Nov 2020 11:44:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201124092445.658647-1-mcascell@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::341; envelope-from=philippe.mathieu.daude@gmail.com; helo=mail-wm1-x341.google.com X-Spam_score_int: -14 X-Spam_score: -1.5 X-Spam_bar: - X-Spam_report: (-1.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.248, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.248, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jasowang@redhat.com, pgn@zju.edu.cn, Laurent Vivier , Finn Thain Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" +Laurent/Finn On 11/24/20 10:24 AM, Mauro Matteo Cascella wrote: > An integer underflow could occur during packet transmission due to 'tx_len' not > being updated if SONIC_TFC register is set to zero. Check for negative 'tx_len' > when removing existing FCS. > > RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1899722 > Signed-off-by: Mauro Matteo Cascella > Reported-by: Gaoning Pan > --- > hw/net/dp8393x.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/hw/net/dp8393x.c b/hw/net/dp8393x.c > index 674b04b354..205c0decc5 100644 > --- a/hw/net/dp8393x.c > +++ b/hw/net/dp8393x.c > @@ -495,6 +495,10 @@ static void dp8393x_do_transmit_packets(dp8393xState *s) > } else { > /* Remove existing FCS */ > tx_len -= 4; > + if (tx_len < 0) { > + SONIC_ERROR("tx_len is %d\n", tx_len); > + break; > + } > } > > if (s->regs[SONIC_RCR] & (SONIC_RCR_LB1 | SONIC_RCR_LB0)) { > Doesn't it make more sense to check 'tx_len >= 4' and skip tx/rx when 'tx_len == 0'? -- >8 -- @@ -488,25 +488,29 @@ static void dp8393x_do_transmit_packets(dp8393xState *s) } } - /* Handle Ethernet checksum */ - if (!(s->regs[SONIC_TCR] & SONIC_TCR_CRCI)) { - /* Don't append FCS there, to look like slirp packets - * which don't have one */ - } else { - /* Remove existing FCS */ - tx_len -= 4; + if (tx_len >= 4) { + /* Handle Ethernet checksum */ + if (!(s->regs[SONIC_TCR] & SONIC_TCR_CRCI)) { + /* Don't append FCS there, to look like slirp packets + * which don't have one */ + } else { + /* Remove existing FCS */ + tx_len -= 4; + } } - if (s->regs[SONIC_RCR] & (SONIC_RCR_LB1 | SONIC_RCR_LB0)) { - /* Loopback */ - s->regs[SONIC_TCR] |= SONIC_TCR_CRSL; - if (nc->info->can_receive(nc)) { - s->loopback_packet = 1; - nc->info->receive(nc, s->tx_buffer, tx_len); + if (tx_len > 0) { + if (s->regs[SONIC_RCR] & (SONIC_RCR_LB1 | SONIC_RCR_LB0)) { + /* Loopback */ + s->regs[SONIC_TCR] |= SONIC_TCR_CRSL; + if (nc->info->can_receive(nc)) { + s->loopback_packet = 1; + nc->info->receive(nc, s->tx_buffer, tx_len); + } + } else { + /* Transmit packet */ + qemu_send_packet(nc, s->tx_buffer, tx_len); } - } else { - /* Transmit packet */ - qemu_send_packet(nc, s->tx_buffer, tx_len); } s->regs[SONIC_TCR] |= SONIC_TCR_PTX; ---