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Fri, 17 Jul 2020 03:10:31 +0000 (UTC) Subject: Re: [PATCH] e1000e: using bottom half to send packets To: Li Qiang , dmitry.fleytman@gmail.com, pbonzini@redhat.com, mst@redhat.com References: <20200716161453.61295-1-liq3ea@163.com> From: Jason Wang Message-ID: <281e3c85-b8eb-0c3e-afc3-41011861b8ea@redhat.com> Date: Fri, 17 Jul 2020 11:10:28 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200716161453.61295-1-liq3ea@163.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=jasowang@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/16 23:10:49 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: liq3ea@gmail.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/7/17 上午12:14, Li Qiang wrote: > Alexander Bulekov reported a UAF bug related e1000e packets send. > > -->https://bugs.launchpad.net/qemu/+bug/1886362 > > This is because the guest trigger a e1000e packet send and set the > data's address to e1000e's MMIO address. So when the e1000e do DMA > it will write the MMIO again and trigger re-entrancy and finally > causes this UAF. > > Paolo suggested to use a bottom half whenever MMIO is doing complicate > things in here: > -->https://lists.nongnu.org/archive/html/qemu-devel/2020-07/msg03342.html > > Reference here: > 'The easiest solution is to delay processing of descriptors to a bottom > half whenever MMIO is doing something complicated. This is also better > for latency because it will free the vCPU thread more quickly and leave > the work to the I/O thread.' I think several things were missed in this patch (take virtio-net as a reference), do we need the following things: - Cancel the bh when VM is stopped. - A throttle to prevent bh from executing too much timer? - A flag to record whether or not this a pending tx (and migrate it?) Thanks > > This patch fixes this UAF. > > Signed-off-by: Li Qiang > --- > hw/net/e1000e_core.c | 25 +++++++++++++++++-------- > hw/net/e1000e_core.h | 2 ++ > 2 files changed, 19 insertions(+), 8 deletions(-) > > diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c > index bcd186cac5..6165b04b68 100644 > --- a/hw/net/e1000e_core.c > +++ b/hw/net/e1000e_core.c > @@ -2423,32 +2423,27 @@ e1000e_set_dbal(E1000ECore *core, int index, uint32_t val) > static void > e1000e_set_tctl(E1000ECore *core, int index, uint32_t val) > { > - E1000E_TxRing txr; > core->mac[index] = val; > > if (core->mac[TARC0] & E1000_TARC_ENABLE) { > - e1000e_tx_ring_init(core, &txr, 0); > - e1000e_start_xmit(core, &txr); > + qemu_bh_schedule(core->tx[0].tx_bh); > } > > if (core->mac[TARC1] & E1000_TARC_ENABLE) { > - e1000e_tx_ring_init(core, &txr, 1); > - e1000e_start_xmit(core, &txr); > + qemu_bh_schedule(core->tx[1].tx_bh); > } > } > > static void > e1000e_set_tdt(E1000ECore *core, int index, uint32_t val) > { > - E1000E_TxRing txr; > int qidx = e1000e_mq_queue_idx(TDT, index); > uint32_t tarc_reg = (qidx == 0) ? TARC0 : TARC1; > > core->mac[index] = val & 0xffff; > > if (core->mac[tarc_reg] & E1000_TARC_ENABLE) { > - e1000e_tx_ring_init(core, &txr, qidx); > - e1000e_start_xmit(core, &txr); > + qemu_bh_schedule(core->tx[qidx].tx_bh); > } > } > > @@ -3322,6 +3317,16 @@ e1000e_vm_state_change(void *opaque, int running, RunState state) > } > } > > +static void e1000e_core_tx_bh(void *opaque) > +{ > + struct e1000e_tx *tx = opaque; > + E1000ECore *core = tx->core; > + E1000E_TxRing txr; > + > + e1000e_tx_ring_init(core, &txr, tx - &core->tx[0]); > + e1000e_start_xmit(core, &txr); > +} > + > void > e1000e_core_pci_realize(E1000ECore *core, > const uint16_t *eeprom_templ, > @@ -3340,6 +3345,8 @@ e1000e_core_pci_realize(E1000ECore *core, > for (i = 0; i < E1000E_NUM_QUEUES; i++) { > net_tx_pkt_init(&core->tx[i].tx_pkt, core->owner, > E1000E_MAX_TX_FRAGS, core->has_vnet); > + core->tx[i].core = core; > + core->tx[i].tx_bh = qemu_bh_new(e1000e_core_tx_bh, &core->tx[i]); > } > > net_rx_pkt_init(&core->rx_pkt, core->has_vnet); > @@ -3367,6 +3374,8 @@ e1000e_core_pci_uninit(E1000ECore *core) > for (i = 0; i < E1000E_NUM_QUEUES; i++) { > net_tx_pkt_reset(core->tx[i].tx_pkt); > net_tx_pkt_uninit(core->tx[i].tx_pkt); > + qemu_bh_delete(core->tx[i].tx_bh); > + core->tx[i].tx_bh = NULL; > } > > net_rx_pkt_uninit(core->rx_pkt); > diff --git a/hw/net/e1000e_core.h b/hw/net/e1000e_core.h > index aee32f7e48..94ddc6afc2 100644 > --- a/hw/net/e1000e_core.h > +++ b/hw/net/e1000e_core.h > @@ -77,6 +77,8 @@ struct E1000Core { > unsigned char sum_needed; > bool cptse; > struct NetTxPkt *tx_pkt; > + QEMUBH *tx_bh; > + E1000ECore *core; > } tx[E1000E_NUM_QUEUES]; > > struct NetRxPkt *rx_pkt;