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Tsirkin" Subject: [PATCH] hw/display/virtio-gpu: validate stride against width on scanout Date: Thu, 16 Jul 2026 00:10:55 +0400 Message-ID: <20260715201055.2465320-1-marcandre.lureau@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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=lists1p.gnu.org; Received-SPF: permerror client-ip=170.10.129.124; envelope-from=marcandre.lureau@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 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=-0.01, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, T_SPF_PERMERROR=0.01 autolearn=no 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: 1784146285791158500 From: Marc-Andr=C3=A9 Lureau Validate that the framebuffer stride is at least width * bytes_per_pixel in both virtio_gpu_scanout_blob_to_fb() and virtio_gpu_do_set_scanout(). A guest can set a very small stride while using a large width. The total size check (offset + stride * height <=3D blob_size) passes because stride * height is small, but pixman reads width * bytes_per_pixel per row, causing heap OOB reads. The leaked data is rendered to the host display. The check is added in virtio_gpu_do_set_scanout() to cover all paths: blob scanout, non-blob scanout and migration post_load. The additional early check in virtio_gpu_scanout_blob_to_fb() rejects invalid blob configurations early. Fixes: CVE-2026-63109 Fixes: 144bd171c837 ("virtio-gpu: Support blob scanout using dmabuf fd") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3989 Signed-off-by: Marc-Andr=C3=A9 Lureau Reported-by: Tristan @TristanInSec Reviewed-by: Akihiko Odaki --- hw/display/virtio-gpu.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c index 89a73793a42..1d4b8ee4192 100644 --- a/hw/display/virtio-gpu.c +++ b/hw/display/virtio-gpu.c @@ -647,6 +647,14 @@ static bool virtio_gpu_do_set_scanout(VirtIOGPU *g, return false; } =20 + if (fb->stride < (uint64_t)fb->width * fb->bytes_pp) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: stride %u too small for width %u at %u bpp\n", + __func__, fb->stride, fb->width, fb->bytes_pp); + *error =3D VIRTIO_GPU_RESP_ERR_INVALID_PARAMETER; + return false; + } + g->parent_obj.enable =3D 1; =20 if (res->blob) { @@ -754,6 +762,14 @@ bool virtio_gpu_scanout_blob_to_fb(struct virtio_gpu_f= ramebuffer *fb, fb->width =3D ss->width; fb->height =3D ss->height; fb->stride =3D ss->strides[0]; + + if (fb->stride < (uint64_t)fb->width * fb->bytes_pp) { + qemu_log_mask(LOG_GUEST_ERROR, + "%s: stride %u too small for width %u at %u bpp\n", + __func__, fb->stride, fb->width, fb->bytes_pp); + return false; + } + fb->offset =3D ss->offsets[0] + ss->r.x * fb->bytes_pp + ss->r.y * fb-= >stride; =20 fbend =3D fb->offset; --=20 2.55.0