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[83.51.215.31]) by smtp.gmail.com with ESMTPSA id l3sm2331270wmh.2.2021.05.20.04.10.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 May 2021 04:10:15 -0700 (PDT) From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= To: qemu-devel@nongnu.org Subject: [RFC PATCH 12/12] hw/virtio: Display error if vring flag field is not aligned Date: Thu, 20 May 2021 13:09:19 +0200 Message-Id: <20210520110919.2483190-13-philmd@redhat.com> X-Mailer: git-send-email 2.26.3 In-Reply-To: <20210520110919.2483190-1-philmd@redhat.com> References: <20210520110919.2483190-1-philmd@redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=philmd@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.39, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: Peter Maydell , "Michael S. Tsirkin" , Richard Henderson , Peter Xu , Bibo Mao , Stefan Hajnoczi , Paolo Bonzini , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Per the virtio spec [*] the vring is aligned, so the 'flag' field is also 16-bit aligned. If it is not, this is a guest error, and we'd rather report any malicious activity. Enforce the transaction alignment by setting the 'aligned' attribute and log unaligned addresses. Signed-off-by: Philippe Mathieu-Daudé --- hw/virtio/virtio.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 1b8bc194ce1..f19d12fc71e 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -291,15 +291,24 @@ static inline bool vring_avail_flags(VirtQueue *vq, uint16_t *val) { VRingMemoryRegionCaches *caches = vring_get_region_caches(vq); hwaddr pa = offsetof(VRingAvail, flags); + MemTxAttrs attrs = { .aligned = 1 }; + MemTxResult res; if (!caches) { *val = 0; return true; } - *val = virtio_lduw_phys_cached_with_attrs(vq->vdev, &caches->avail, pa); + *val = virtio_lduw_phys_cached_with_attrs(vq->vdev, &caches->avail, + pa, attrs, &res); + if (res == MEMTX_UNALIGNED_ERROR) { + qemu_log_mask(LOG_GUEST_ERROR, + "virtio: vring flag address 0x%" HWADDR_PRIX " " + "is not aligned\n", pa); + return false; + } - return true; + return res == MEMTX_OK; } /* Called within rcu_read_lock(). */ -- 2.26.3