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Tsirkin" To: Jason Wang Subject: Re: [PATCH] virtio-net: check the existence of peer before accesing its config Message-ID: <20200727073943-mutt-send-email-mst@kernel.org> References: <20200727074328.2279-1-jasowang@redhat.com> <20200727053954-mutt-send-email-mst@kernel.org> <20200727115322.4e7fe1aa.cohuck@redhat.com> <20200727061112-mutt-send-email-mst@kernel.org> <0cad868a-7f64-47e0-f4bf-014a5fc1bcf6@redhat.com> MIME-Version: 1.0 In-Reply-To: <0cad868a-7f64-47e0-f4bf-014a5fc1bcf6@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=mst@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/27 01:46:13 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: Cornelia Huck , qemu-devel@nongnu.org, Cindy Lu Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Jul 27, 2020 at 06:26:37PM +0800, Jason Wang wrote: > > On 2020/7/27 下午6:13, Michael S. Tsirkin wrote: > > On Mon, Jul 27, 2020 at 11:53:22AM +0200, Cornelia Huck wrote: > > > On Mon, 27 Jul 2020 05:41:17 -0400 > > > "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? > > > Same as with a non-vdpa peer? It's the dereference that needs to be > > > guarded. > > So vdpa has a GET_CONFIG ioctl which to me hints that a peer needs to be > > notified on get config calls. > > If we return config from qemu memory here, then I guess we > > need to call GET_CONFIG on connect and validate it - > > does this make sense? > > > > Cindy, Jason? > > > For "connect" you meant connecting virtio-net to its peer (vDPA)? AFAIK, if > we start with no peer, there's no way to set a peer afterwards. > > Thanks That would be a good sentence to add in a code comment: /* * Is this VDPA? No peer means not VDPA: there's no way to * disconnect/reconnect a VDPA peer. */ > > > > > > > A code comment might be helpful here. > > > > > > > > > --- > > > > > hw/net/virtio-net.c | 22 +++++++++++----------- > > > > > 1 file changed, 11 insertions(+), 11 deletions(-)