From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793878991; b=bCSWsjZg5SOlWcGujDsl+y4pIYnADJW4Koe1mbxB7xq6dPC3N8QzjwYDi3uO5gGcMM3A IMtGv2xCmJpQQsMKQ0JiTvrfGLVt56C8Q3WPrZoX4y3TTQUJ3IcB0dYWC4T2+nPFm8/oJ q8huYXOc0AGsktH6x0UQrqfX8GyK53LbZekKoirP1urUH2icVliIhE10+yHC4nuEvj6Rd gl3okf+kLsWQSXUxPd2gwH9lRnyxREXoiuzGrQ1tkkWSiU5gCrXWB2OOntYEO6ADVNWeN xM4XkIf932juBzMuyLlxjLYbXxUzmcZZLxYbOW9TrzHY7ciz+JLIFXX9AiZigZk+dvQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793878991; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Type:X-Mailer: Content-Transfer-Encoding; bh=To1pchWJNq8O58SS1SPMwu0h1sZmzD6KnBh+BH7g+b8=; b=MvIcgBaURN8D/PhJkpo1YbdiY8t8Bf+vcW4EqPsKuUJX6miaOeD0TQ6NBIBeeEoxhnv0 AR2c+SEvtBsrlonPcsTbpSUQOaQqvRruMmyVcrN5FxbhZ/GNcm9yTnepHJWSsO08FtK0z HHbfBrwPV7v9GUq00YwRhBYAYq6nNA8vysiRGSahkgUVqjBjdt5ALJm8Q6CPlOLyF7V3r UujouEohOvYH4pN06leeyzoRIwmC4PfiCkGBbWxmRhFtcRxQzSuhUKv62zsjVMMORjG90 LjoKIPH5acC/wvRetaXztjcjy/z9ssLDUDTub/hQVfV3/PXFDWdWnANLCB/vER8La2Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PYJ0DDWi; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 91AD660A2630; Thu, 5 Nov 2026 11:43:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PYJ0DDWi Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DA9A1F000C1; Thu, 5 Nov 2026 11:43:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793878991; bh=To1pchWJNq8O58SS1SPMwu0h1sZmzD6KnBh+BH7g+b8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PYJ0DDWicQT5hXAFcIfiX/QnAroRb6yU1aQNeVFnaiUwm0lU2m0vwts4DphsnsxBh oQ50LpLcoIa8LeO9Bt7JHPIWz3Gt0A5agsosplf/v3xDDnG1tmZb0B3zg6Z/NyhYFA /wWFAGdL38tmhOsqIauGcW3fwlS6rMaT5OlHJR5j3Xfbujkpg2ZxBBxb0x8aHiDFjj 7m9OY9ZpYfvOBEYCnhQ9lPg90teUbhVvpP/tPkKbI6xfN9ZqI/+kjmOgGe4ZbKC9tM acekT8pcraLHM4BSD2eYyns4AxrPr1AU74fwLyfn0B1JuvKq5z0NnXNs1F5gFOAEk+ bcoLd8Zd0g4xw== From: Leon Romanovsky To: Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Dmitry Torokhov , Andrew Lunn , Heiner Kallweit , Russell King , "David S. Miller" , Jakub Kicinski , Paolo Abeni , Johannes Berg , Jonathan Corbet , Shuah Khan , Randy Dunlap , Bjorn Helgaas , "Joerg Roedel (AMD)" , Suravee Suthikulpanit , Vasant Hegde , Will Deacon , Robin Murphy , David Woodhouse , Lu Baolu , Johan Hovold , Eric Dumazet , Marcel Holtmann , Luiz Augusto von Dentz , Nipun Gupta , Nikhil Agarwal , Pieter Jansen van Vuuren Cc: linux-kernel@vger.kernel.org, driver-core@lists.linux.dev, linux-input@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, linux-usb@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, iommu@lists.linux.dev, Jason Gunthorpe Subject: [PATCH 10/17] driver core: Expose device trust authorization through sysfs Date: Thu, 5 Nov 2026 13:42:23 +0200 Message-ID: <20261105-device-trust-core-v1-10-1e536825b4eb@nvidia.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261105-device-trust-core-v1-0-1e536825b4eb@nvidia.com> References: <20261105-device-trust-core-v1-0-1e536825b4eb@nvidia.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.15-dev-18f8f Content-Transfer-Encoding: 8bit From: Leon Romanovsky An initrd must authorize a disabled device after attestation even if a built-in driver already attempted to probe it. Expose requested trust_policy and read-only active trust. Allow explicit disabled policy to advance once to adversary or full, fixing that decision immediately. Reject later policy changes, including for a device claimed before registration, while allowing same-value writes on live devices. Keep initial unrestricted selection separate from explicit authorization and bind-time commitment. Serialize writes with probing under the device lock. Include the attributes in device ownership changes. Signed-off-by: Leon Romanovsky --- Documentation/ABI/testing/sysfs-devices-trust | 51 +++++++++++++ MAINTAINERS | 1 + drivers/base/base.h | 6 ++ drivers/base/core.c | 15 +++- drivers/base/trust.c | 102 ++++++++++++++++++++++++++ 5 files changed, 174 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/sysfs-devices-trust b/Documentation/ABI/testing/sysfs-devices-trust new file mode 100644 index 0000000000000..97e07a174769c --- /dev/null +++ b/Documentation/ABI/testing/sysfs-devices-trust @@ -0,0 +1,51 @@ +What: /sys/devices/.../trust +Date: September 2026 +Contact: driver-core@lists.linux.dev +Description: + (RO) The active trust level for the device. The values are + "disabled", "adversary", and "full". Driver core resolves + the level before DMA configuration and probe, and retains it + through removal and DMA cleanup. Outside a bind transaction + the level is "disabled". This does not imply that policy is + writable or that the device has never operated. + +What: /sys/devices/.../trust_policy +Date: September 2026 +Contact: driver-core@lists.linux.dev +Description: + (RW) The requested trust policy for the device. The initial + value may be selected by the bus before the device is + registered; otherwise it is "default". The policy is resolved + to an active trust level before the device is probed. + + The values are "default", "disabled", "adversary", and + "full". "default" lets the bus select the active trust level. + "disabled" prevents a functional driver from binding. + "adversary" requests operation with the restrictions that the + bus and DMA layers can enforce for a potentially malicious + device; it does not isolate DMA by itself. "full" requests + normal operation. + + Before an operating level is committed, policy may change + freely until "disabled" is selected. Explicit "disabled" + blocks binding while allowing a later write of "adversary" or + "full". Repeated rejected probes preserve this opportunity. + Authorization immediately fixes the requested policy. + Returning to "default" or "disabled", or selecting another + mode, fails. + + Successful resolution to an allowed level commits policy + and operating level before driver or DMA setup. Both remain + fixed for the device object's lifetime, including through + failed or deferred probes, unbind, reset, and driver reload. + Later binds must resolve to the same level, including when + the policy is "default". A resolver error or disabled result + before commitment leaves the policy's writability unchanged. + + For a live device, writing the existing value succeeds + without changing state. Other forbidden writes fail with + EBUSY; invalid strings fail with EINVAL. Removed devices + reject writes with ENODEV. Writes do not trigger probing or + attestation. + Queued probes may proceed immediately after authorization, + so userspace must complete verification before granting it. diff --git a/MAINTAINERS b/MAINTAINERS index b726344362b41..a145aaaca2ef3 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -8150,6 +8150,7 @@ L: driver-core@lists.linux.dev S: Supported T: git git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git F: Documentation/ABI/testing/sysfs-bus-drivers-probe +F: Documentation/ABI/testing/sysfs-devices-trust F: Documentation/core-api/kobject.rst F: Documentation/driver-api/driver-model/ F: drivers/base/ diff --git a/drivers/base/base.h b/drivers/base/base.h index 4683b9c2a8d83..c88b3302969f2 100644 --- a/drivers/base/base.h +++ b/drivers/base/base.h @@ -180,6 +180,12 @@ void bus_remove_driver(struct device_driver *drv); void device_release_driver_internal(struct device *dev, const struct device_driver *drv, struct device *parent); +extern const struct attribute_group device_trust_attr_group; + +#if IS_ENABLED(CONFIG_KUNIT) +int device_trust_set_policy(struct device *dev, enum device_trust_policy policy); +#endif + /* All active trust level transitions are serialized by the device lock. */ void device_trust_init_state(struct device *dev); int device_trust_prepare(struct device *dev, const struct device_driver *drv); diff --git a/drivers/base/core.c b/drivers/base/core.c index a0ffe74993677..dca0179714c82 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -2989,10 +2989,14 @@ static int device_add_attrs(struct device *dev) if (error) goto err_remove_type_groups; + error = device_add_group(dev, &device_trust_attr_group); + if (error) + goto err_remove_dev_groups; + if (device_supports_offline(dev) && !dev_offline_disabled(dev)) { error = device_create_file(dev, &dev_attr_online); if (error) - goto err_remove_dev_groups; + goto err_remove_dev_trust_group; } if (fw_devlink_flags && !fw_devlink_is_permissive() && dev->fwnode) { @@ -3022,6 +3026,8 @@ static int device_add_attrs(struct device *dev) device_remove_file(dev, &dev_attr_waiting_for_supplier); err_remove_dev_online: device_remove_file(dev, &dev_attr_online); + err_remove_dev_trust_group: + device_remove_group(dev, &device_trust_attr_group); err_remove_dev_groups: device_remove_groups(dev, dev->groups); err_remove_type_groups: @@ -3047,6 +3053,7 @@ static void device_remove_attrs(struct device *dev) device_remove_file(dev, &dev_attr_removable); device_remove_file(dev, &dev_attr_waiting_for_supplier); device_remove_file(dev, &dev_attr_online); + device_remove_group(dev, &device_trust_attr_group); device_remove_groups(dev, dev->groups); if (type) @@ -4790,6 +4797,12 @@ static int device_attrs_change_owner(struct device *dev, kuid_t kuid, if (error) return error; + /* Change the trust attributes of @dev to @kuid/@kgid. */ + error = sysfs_group_change_owner(kobj, &device_trust_attr_group, kuid, + kgid); + if (error) + return error; + if (device_supports_offline(dev) && !dev_offline_disabled(dev)) { /* Change online device attributes of @dev to @kuid/@kgid. */ error = sysfs_file_change_owner(kobj, dev_attr_online.attr.name, diff --git a/drivers/base/trust.c b/drivers/base/trust.c index 10a135b8bf399..884e7c2dfbbb6 100644 --- a/drivers/base/trust.c +++ b/drivers/base/trust.c @@ -3,6 +3,7 @@ #include #include #include +#include #include #include "base.h" @@ -122,3 +123,104 @@ bool device_is_adversarial(const struct device *dev) return device_get_trust_level(dev) == DEVICE_TRUST_ADVERSARY; } EXPORT_SYMBOL_GPL(device_is_adversarial); + +static const char * const device_trust_policy_names[] = { + [DEVICE_TRUST_POLICY_DEFAULT] = "default", + [DEVICE_TRUST_POLICY_DISABLED] = "disabled", + [DEVICE_TRUST_POLICY_ADVERSARY] = "adversary", + [DEVICE_TRUST_POLICY_FULL] = "full", +}; + +static const char * const device_trust_level_names[] = { + [DEVICE_TRUST_DISABLED] = "disabled", + [DEVICE_TRUST_ADVERSARY] = "adversary", + [DEVICE_TRUST_FULL] = "full", +}; + +static ssize_t trust_show(struct device *dev, + const struct device_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%s\n", + device_trust_level_names[device_get_trust_level(dev)]); +} +static DEVICE_ATTR_RO(trust); + +static ssize_t trust_policy_show(struct device *dev, + const struct device_attribute *attr, char *buf) +{ + return sysfs_emit(buf, "%s\n", + device_trust_policy_names[READ_ONCE(dev->trust_policy)]); +} + +VISIBLE_IF_KUNIT int device_trust_set_policy(struct device *dev, + enum device_trust_policy policy) +{ + int ret = 0; + + if (policy < DEVICE_TRUST_POLICY_DEFAULT || + policy > DEVICE_TRUST_POLICY_FULL) + return -EINVAL; + + device_lock(dev); + if (dev->p->dead) { + ret = -ENODEV; + goto unlock; + } + if (policy == dev->trust_policy) + goto unlock; + + /* A driver that claimed the device before registration was not admitted. */ + if (READ_ONCE(dev->driver)) { + ret = -EBUSY; + goto unlock; + } + + switch (dev->p->trust_state) { + case DEVICE_TRUST_SELECTABLE: + if (policy == DEVICE_TRUST_POLICY_DISABLED) + dev->p->trust_state = DEVICE_TRUST_WAITING; + break; + case DEVICE_TRUST_WAITING: + if (policy != DEVICE_TRUST_POLICY_ADVERSARY && + policy != DEVICE_TRUST_POLICY_FULL) { + ret = -EBUSY; + goto unlock; + } + dev->p->trust_state = DEVICE_TRUST_AUTHORIZED; + break; + default: + ret = -EBUSY; + goto unlock; + } + WRITE_ONCE(dev->trust_policy, policy); +unlock: + device_unlock(dev); + return ret; +} +EXPORT_SYMBOL_IF_KUNIT(device_trust_set_policy); + +static ssize_t trust_policy_store(struct device *dev, + const struct device_attribute *attr, + const char *buf, size_t count) +{ + int policy, ret; + + policy = sysfs_match_string(device_trust_policy_names, buf); + if (policy < 0) + return policy; + + ret = device_trust_set_policy(dev, policy); + + return ret ? ret : count; +} +static DEVICE_ATTR_RW(trust_policy); + +static struct attribute *device_trust_attrs[] = { + &dev_attr_trust.attr, + &dev_attr_trust_policy.attr, + NULL, +}; + +const struct attribute_group device_trust_attr_group = { + .attrs = device_trust_attrs, +}; -- 2.56.0