From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3DE0718FDDB for ; Thu, 11 Dec 2025 04:59:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765429170; cv=pass; b=r+CulWREUWzJM9O7NTnwZtzxPfxShPUT820EBf70bI7HRKSOXPSX9p9Ba0C78h6ZAVdoF/uib01aR9atjBwJpgd8looNJv6c28ia3UTmv3nc5pJs4rt7CGJFGaZCi8hsrITrRA+fgSiJrSMIMIipiTNj783k4frGGuwp+aEIon4= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765429170; c=relaxed/simple; bh=9Wr8elOShctkOD9AqVLPgycqaZObJzFqDnlh4FRkYvU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=VHH8fMvXe1XzcJwQkcBOmb5G3KeqbBPSbqZYB60BD5pg1xR//1F1hQvBdsmQIWMyhOHq0CtOdb/7YqvLlG+97tgxbAAJMNluZGpghtW7184tvT+NbpG2cHEVGxt52PAc7YsG4YkQnzuBF6wL1xW97mp/fcrTsAN2vPjc1tehRA4= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=dmitry.osipenko@collabora.com header.b=HY3aHcLR; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=dmitry.osipenko@collabora.com header.b="HY3aHcLR" ARC-Seal: i=1; a=rsa-sha256; t=1765429147; cv=none; d=zohomail.com; s=zohoarc; b=mpRRoGYWy0CaWZFxvKQ2CXqkwG07kRC8GtCV/AV39794kpUk/tR/uWAr7a/I+YSCBVnWiWn2/LfUKVONQJuZbV/sGFvkKj8wohVH5zksSP+J5IZjO1ncRBOGQfGYGHbz+08PUOiQmB86Iy0DJzAeNGg3If9Ef9Cn0/LwIIUmB84= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1765429147; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=qwwDK7ES44/mxuRZWvi5JZL/SkS9OB3I5PC49lDpPF4=; b=ldPbMMhVfRjkxcYRy7uIyhLia/OUNKBJjgDGFkw143Hs2tx/zo/hTWTr7Vp45RW7hZsdPia/vaiaglExsdFsMrRS1vJAqMHuDU8n/8pbtBCTED6r2P6hHiWxH0T7Kn/gxvnD0p1gm3xL2eWf27tC+o+JEtjhDiRG+M7X7okuGbg= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=dmitry.osipenko@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1765429146; s=zohomail; d=collabora.com; i=dmitry.osipenko@collabora.com; h=Message-ID:Date:Date:MIME-Version:Subject:Subject:To:To:Cc:Cc:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=qwwDK7ES44/mxuRZWvi5JZL/SkS9OB3I5PC49lDpPF4=; b=HY3aHcLRkXFX9kMvwxviOrWM3TP/YIhH5U0oxpPcMzIS93U7mYJzJKXTmltT7Bxe 4tgInjqY+T8a8s8lAhEedR6Cg0SKFpmJjK/+VrK4Vww5Q4RQvmqRQ5QPh52lcSwZl8Y Lq5TCDJCUXe8mdsaFqnMFfPovjO6QJsEixiI1fZk= Received: by mx.zohomail.com with SMTPS id 1765429145328519.7374459440082; Wed, 10 Dec 2025 20:59:05 -0800 (PST) Message-ID: <61a12a08-86bf-498f-8e3e-a49a91c1bbd1@collabora.com> Date: Thu, 11 Dec 2025 07:58:57 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/virtio: fix undefined behavior in capset shift calculation To: Alexey Simakov , David Airlie Cc: Gerd Hoffmann , Gurchetan Singh , Chia-I Wu , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Simona Vetter , Lingfeng Yang , dri-devel@lists.freedesktop.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, lvc-project@linuxtesting.org References: <20251208160228.13145-1-bigalex934@gmail.com> Content-Language: en-US From: Dmitry Osipenko In-Reply-To: <20251208160228.13145-1-bigalex934@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ZohoMailClient: External On 12/8/25 19:02, Alexey Simakov wrote: > According to MAX_CAPSET_ID, possible values of vgdev->capsets[i].id > range from 0 to 63. Since the intermediate calculation uses type int, > shifting by values larger than the bit width of int is undefined > behavior as per the C language standard. > > Explicitly cast the left-shift operand to ULL to prevent undefined > behavior during the calculation. > > Found by Linux Verification Center (linuxtesting.org) with Svace. > > Fixes: 1925d6a7e0f4 ("drm/virtio: implement context init: track valid capabilities in a mask") > Signed-off-by: Alexey Simakov > --- > drivers/gpu/drm/virtio/virtgpu_kms.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c > index 1c15cbf326b7..2e0ec7590ac2 100644 > --- a/drivers/gpu/drm/virtio/virtgpu_kms.c > +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c > @@ -104,7 +104,7 @@ static void virtio_gpu_get_capsets(struct virtio_gpu_device *vgdev, > return; > } > > - vgdev->capset_id_mask |= 1 << vgdev->capsets[i].id; > + vgdev->capset_id_mask |= 1ULL << vgdev->capsets[i].id; > DRM_INFO("cap set %d: id %d, max-version %d, max-size %d\n", > i, vgdev->capsets[i].id, > vgdev->capsets[i].max_version, Reviewed-by: Dmitry Osipenko -- Best regards, Dmitry