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Tsirkin" To: Peter Maydell Cc: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Junjie Cao , qemu-devel@nongnu.org, jasowang@redhat.com, yuri.benditovich@daynix.com, akihiko.odaki@daynix.com, qemu-stable@nongnu.org Subject: Re: [PATCH] virtio-net: validate RSS indirections_len in post_load Message-ID: <20260323095706-mutt-send-email-mst@kernel.org> References: <20260323131531.1976-1-junjie.cao@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Mar 23, 2026 at 01:53:53PM +0000, Peter Maydell wrote: > On Mon, 23 Mar 2026 at 13:43, Daniel P. Berrangé wrote: > > > > On Mon, Mar 23, 2026 at 09:15:31PM +0800, Junjie Cao wrote: > > > virtio_net_handle_rss() enforces that indirections_len is a non-zero > > > power of two no larger than VIRTIO_NET_RSS_MAX_TABLE_LEN, but > > > virtio_net_rss_post_load() applies none of these checks to values > > > restored from the migration stream. > > > > > > A crafted migration stream can set indirections_len to 0. Even if it > > > > The migration stream originating from the source QEMU is trusted. > > Is it? In https://www.qemu.org/docs/master/system/security.html we say: > > # The following entities are untrusted, meaning that they may be buggy > # or malicious: > > # * Guest > # * User-facing interfaces (e.g. VNC, SPICE, WebSocket) > # * Network protocols (e.g. NBD, live migration) > # * User-supplied files (e.g. disk images, kernels, device trees) > # * Passthrough devices (e.g. PCI, USB) > > which explicitly lists "live migration" as an untrusted entity. > > I would definitely be extremely cautious about having a threat > model where I had to distrust inbound migration data, but the > above does suggest we aim to handle that, and we have I think > in the past taken patches which add sanity-checking to the > migration data. > > thanks > -- PMM And we even assigned a low priority CVEs to these.