From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f42.google.com (mail-wm1-f42.google.com [209.85.128.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8574633ADAF for ; Thu, 3 Sep 2026 07:19:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.42 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788419993; cv=none; b=txn+Yg+GMiwWRHKgSgwiUhZYDQ24XdOKfhFeDq+FSPWsPlMRtWtlEdVvn25UziUnTn9fXyKKkUpa6jdyr6DBOiLFkpsyoYfQc+fLVovMG4yow7ovmYJYlvBs56bb9h259kNTOKYMqFPCGSjOfAdJxny3d/KddLshP2QIxj2a9Wc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788419993; c=relaxed/simple; bh=bID5YgkMDYkgq+pAjBhjxhgYCZAT4H5TMvdFWMAkwBM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=MxUNzwFrvJ4k2WbOTSzagulUW28MrMULKujscz/2Kl8cYYFA8xJJO0Z8P/xbACN+eCq2s9JHDWsI6051TpmFuzUeMt4s5zivZwtw4v1ZjIZyV78nhCTh0WsGVKH5ejBS3VBMkH97ZURtgq2u4xKWCJ3OIFrZYlqxmrkAzVT6q+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=QRas2Paq; arc=none smtp.client-ip=209.85.128.42 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QRas2Paq" Received: by mail-wm1-f42.google.com with SMTP id 5b1f17b1804b1-49b9320423cso19856945e9.0 for ; Thu, 03 Sep 2026 00:19:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1788419990; x=1789024790; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=J5t+7VLBXCfNlaP9aaNyIt7RbKcSoQg0nvLVhl0jatU=; b=QRas2PaqID+FMny+GfJ7m2ORG+5e+wOGyM4nsDH3YzXwpEQzNRSyLHiZe9aeGfCOu+ CATgtqnW5pKmGcNHhasgX8Av4soKMJiPMC0ztxUB+meUQGofB0pOKUD9atvcOeQLgU2L 3VZuvAl3Xz7urbjv+rL+jGcoBsyEjNQ/CmrjGbi0JJ67wf5/e5+pxnaKFJSeoxLGPLKs G01F1H0KFEjuIvDsQ7L2Jb5X7HIAq4/9LuxjeZPzGIFzGRSDyUgQ2GYWUyLUlQc1Cb0/ rsq3HhM7+PcNVB/nRSAm2C/6H9nxC13JfCq2ZgOYXAKTUl6/CFGDd5oMoJ/vEHoyl3Lj lECw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788419990; x=1789024790; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=J5t+7VLBXCfNlaP9aaNyIt7RbKcSoQg0nvLVhl0jatU=; b=eMEZOUcEH8heN5ZVxPIWxu9yUGY/SHWVUMvFgaXa/ZuZhYtd7uqK/EQERBI/UfJ8z0 H9PJCGKIUhYlm1gvQFNF8yFvqoiJZ4FAY17kZ8eErqNyFp2XU7699Ro7MsGf84u9Kifl fg4EJQa5r/hv24rB+gPA2CS9v8mtWBQW6NwKFNSCI9Ydxk9ma/AFA60TKseJkwhUVxt0 E8CCWFqJyPML7MEdrMDS1IS3g+t4ThFZ5ExV8bFL9z/WGgcHqseSh7aeFT+ATd4NODag E6+sDGwI8SmurPw9X2Dm6O5NO+jNNJO8vmyAuhK/ZeCqI+U9RMwyRirEY+4CM6PflUM4 dmPA== X-Forwarded-Encrypted: i=1; AKwUvBy465fh77pDoYfR3HNzslkufiS/Ua9WY/v6Cgfecv7usZ1d9u1YMl6r42VmKZ5WYuMsUBEtIt35dE1LoHM=@vger.kernel.org X-Gm-Message-State: AFuF++ktprz+YNQRnlr+sEB67KuQZL3taJVBjYzp8jnsewXXXn3kaTXP 7eApCxIwZnVuNROAHvkkmhLkNjs6gvipiRnisza38jYVEoXBTjw9J1xYDGjhOw== X-Gm-Gg: AYBFou2HuRlJVpdeLEGHn6lCu2yOSgIwCmbxL5jg8pdEouYvBKeouBefc4k6XoGhgEF 5UeSxtNAQU/YQaS8YjpjJP6QIJGZQsW90D3plGRjcRcl/P5LcBAYwNMsyBt2rfHEHE9emyoaP4A +YmIjkulbw0gsi3LD/+tYxnF//MBeqq9tipzFcwoVpK3ge+whj5CMRLSvdOJWHOE2T4fzsLT7Mw RRk+447DyKxDiptd2D117xzgODi+18B9tqq4h0hVUQQq9zV7LrmVcQd5M/iNeHDJ9FfAB4xYAJH B+UlnSS/ZdLHZ8qOybTQKH3C4UpFxGC2TM7csNTbao0s7GeeuIpptJ+bWQ5R0q2Kc9lYYtugMcS Qqym17BPChgUA9fcWgeoNQxXf9BZvveY54msK0ajbRUt5X3bu8qCqys0mhw5uc5MOmZ/6UTZwfX wc00cCiGjJGnmKuinQ4QxqtZ6ghNTgOsP179GniGHN1Md7aXYEIRLf+HBDGTWh28ebOws= X-Received: by 2002:a05:600c:699b:b0:49b:9205:45b3 with SMTP id 5b1f17b1804b1-49ce584c6femr181458935e9.15.1788419989424; Thu, 03 Sep 2026 00:19:49 -0700 (PDT) Received: from SurHub.localdomain ([196.188.114.38]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48448e80745sm11859711f8f.15.2026.09.03.00.19.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 00:19:48 -0700 (PDT) From: Abdifatah Suruur To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Ioana Ciornei , Alex Williamson Subject: [PATCH v2] vfio/fsl-mc: prevent read-only region mappings from becoming writable Date: Thu, 3 Sep 2026 10:19:46 +0300 Message-ID: <20260903071946.13116-1-suruurism@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vfio_fsl_mc_mmap() rejects writable mappings of regions without the WRITE flag, but leaves VM_MAYWRITE set. Userspace can map such a region read-only and then upgrade the mapping to writable with mprotect(). Clear VM_MAYWRITE for regions without the WRITE flag, as i915 does for its read-only objects and as fixed in drm/vc4 (CVE-2026-68445), drm/panthor (CVE-2024-53071) and ptp: vmclock (commit a5edadbae57e2298a56cf7a4e774a027905a331f). Note this is defensive hardening: the fsl-mc bus publishes all device regions with the WRITE flag set, so no device can currently reach the read-only path. The guard costs nothing and keeps the mmap() interface honest if a read-only region ever appears. Fixes: fb1ff4c194157 ("vfio/fsl-mc: Add VFIO framework skeleton for fsl-mc devices") Signed-off-by: Abdifatah Suruur --- v2: commit log now states plainly that the read-only path is unreachable in practice, per Alex's review; dropped Cc: stable as there is no reachable issue to backport. --- a/drivers/vfio/fsl-mc/vfio_fsl_mc.c +++ b/drivers/vfio/fsl-mc/vfio_fsl_mc.c @@ -406,7 +406,11 @@ if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_WRITE) && (vma->vm_flags & VM_WRITE)) return -EINVAL; + /* Prevent read-only region mappings from being upgraded with mprotect() */ + if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_WRITE)) + vm_flags_clear(vma, VM_MAYWRITE); + vma->vm_private_data = mc_dev; return vfio_fsl_mc_mmap_mmio(vdev->regions[index], vma); }