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Tsirkin" References: <20200727074328.2279-1-jasowang@redhat.com> <20200727053954-mutt-send-email-mst@kernel.org> <20200727061812-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <2a5a78a4-1e7b-7d15-2663-52d7b7db6cfe@redhat.com> Date: Mon, 27 Jul 2020 18:23:21 +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: <20200727061812-mutt-send-email-mst@kernel.org> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 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=207.211.31.81; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/27 03:37:14 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: Cornelia Huck , qemu-devel@nongnu.org, Cindy Lu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/7/27 下午6:21, Michael S. Tsirkin wrote: > On Mon, Jul 27, 2020 at 05:49:47PM +0800, Jason Wang wrote: >> On 2020/7/27 下午5:41, Michael S. Tsirkin wrote: >>> On Mon, Jul 27, 2020 at 03:43:28PM +0800, Jason Wang wrote: >>>> We try to get config from peer unconditionally which may lead NULL >>>> pointer dereference. Add a check before trying to access the config. >>>> >>>> Fixes: 108a64818e69b ("vhost-vdpa: introduce vhost-vdpa backend") >>>> Cc: Cindy Lu >>>> Tested-by: Cornelia Huck >>>> Signed-off-by: Jason Wang >>> I am a bit lost here. Isn't this invoked >>> when guest attempts to read the config? >>> With no peer, what do we return to guest? >> >> With no peer, it just work as in the past (read from the qemu's own emulated >> config space). With a vDPA as its peer, it tries to read it from vhost-vDPA. >> >> >>> A code comment might be helpful here. >> >> Does something like above help? >> >> Thanks > I think this part of commit log caused confusion: > > Add a check before trying to access the config. > > looking more at the code, imho in fact here is a better description of > what is going on: > > We try to check whether a peer is VDPA in order to get config from > there - with no peer, this leads to a NULL > pointer dereference. Add a check before trying to access the peer > type. No peer means not VDPA. Yes, this looks much better. Thanks > > >>>> --- >>>> hw/net/virtio-net.c | 22 +++++++++++----------- >>>> 1 file changed, 11 insertions(+), 11 deletions(-) >>>> >>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c >>>> index 4895af1cbe..935b9ef5c7 100644 >>>> --- a/hw/net/virtio-net.c >>>> +++ b/hw/net/virtio-net.c >>>> @@ -125,6 +125,7 @@ static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config) >>>> { >>>> VirtIONet *n = VIRTIO_NET(vdev); >>>> struct virtio_net_config netcfg; >>>> + NetClientState *nc = qemu_get_queue(n->nic); >>>> int ret = 0; >>>> memset(&netcfg, 0 , sizeof(struct virtio_net_config)); >>>> @@ -142,13 +143,12 @@ static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config) >>>> VIRTIO_NET_RSS_SUPPORTED_HASHES); >>>> memcpy(config, &netcfg, n->config_size); >>>> - NetClientState *nc = qemu_get_queue(n->nic); >>>> - if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { >>>> + if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { >>>> ret = vhost_net_get_config(get_vhost_net(nc->peer), (uint8_t *)&netcfg, >>>> - n->config_size); >>>> - if (ret != -1) { >>>> - memcpy(config, &netcfg, n->config_size); >>>> - } >>>> + n->config_size); >>>> + if (ret != -1) { >>>> + memcpy(config, &netcfg, n->config_size); >>>> + } >>>> } >>>> } >>>> @@ -156,6 +156,7 @@ static void virtio_net_set_config(VirtIODevice *vdev, const uint8_t *config) >>>> { >>>> VirtIONet *n = VIRTIO_NET(vdev); >>>> struct virtio_net_config netcfg = {}; >>>> + NetClientState *nc = qemu_get_queue(n->nic); >>>> memcpy(&netcfg, config, n->config_size); >>>> @@ -166,11 +167,10 @@ static void virtio_net_set_config(VirtIODevice *vdev, const uint8_t *config) >>>> qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac); >>>> } >>>> - NetClientState *nc = qemu_get_queue(n->nic); >>>> - if (nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { >>>> - vhost_net_set_config(get_vhost_net(nc->peer), (uint8_t *)&netcfg, >>>> - 0, n->config_size, >>>> - VHOST_SET_CONFIG_TYPE_MASTER); >>>> + if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { >>>> + vhost_net_set_config(get_vhost_net(nc->peer), >>>> + (uint8_t *)&netcfg, 0, n->config_size, >>>> + VHOST_SET_CONFIG_TYPE_MASTER); >>>> } >>>> } >>>> -- >>>> 2.20.1