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Tsirkin" To: qemu-devel@nongnu.org Cc: Peter Maydell , Joelle van Dyne , Akihiko Odaki , Alex =?utf-8?Q?Benn=C3=A9e?= , Dmitry Osipenko Subject: [PULL 41/51] virtio-gpu-virgl: correct parent for blob memory region Message-ID: <81cb15cf3774140da7c17341018a3852f920acb5.1770231744.git.mst@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; 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_H2=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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1770232164829158500 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Joelle van Dyne When `owner` =3D=3D `mr`, `object_unparent` will crash: object_unparent(mr) -> object_property_del_child(mr, mr) -> object_finalize_child_property(mr, name, mr) -> object_unref(mr) -> object_finalize(mr) -> object_property_del_all(mr) -> object_finalize_child_property(mr, name, mr) -> object_unref(mr) -> fail on g_assert(obj->ref > 0) However, passing a different `owner` to `memory_region_init` does not work. `memory_region_ref` has an optimization where it takes a ref only on the owner. That means when flatviews are created, it does not take a ref on the region and you can get a UAF from `flatview_destroy` called from RCU. The correct fix therefore is to use `NULL` as the name which will set the `owner` but not the `parent` (which is still NULL). This allows us to use `memory_region_ref` on itself while not having to rely on unparent for cleanup. Signed-off-by: Joelle van Dyne Reviewed-by: Akihiko Odaki Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Message-Id: <20260103214400.71694-1-j@getutm.app> --- hw/display/virtio-gpu-virgl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c index 07f6355ad6..6a83fb63c8 100644 --- a/hw/display/virtio-gpu-virgl.c +++ b/hw/display/virtio-gpu-virgl.c @@ -120,7 +120,7 @@ virtio_gpu_virgl_map_resource_blob(VirtIOGPU *g, vmr->g =3D g; =20 mr =3D &vmr->mr; - memory_region_init_ram_ptr(mr, OBJECT(mr), "blob", size, data); + memory_region_init_ram_ptr(mr, OBJECT(mr), NULL, size, data); memory_region_add_subregion(&b->hostmem, offset, mr); memory_region_set_enabled(mr, true); =20 @@ -186,7 +186,7 @@ virtio_gpu_virgl_unmap_resource_blob(VirtIOGPU *g, /* memory region owns self res->mr object and frees it by itself */ memory_region_set_enabled(mr, false); memory_region_del_subregion(&b->hostmem, mr); - object_unparent(OBJECT(mr)); + object_unref(OBJECT(mr)); } =20 return 0; --=20 MST