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Message-ID: <c8f189e6-c79b-429a-ab36-2193bb68e3e9@schaufler-ca.com>
Date: Fri, 20 Oct 2023 15:20:58 -0700
From: Casey Schaufler <casey@...aufler-ca.com>
To: Maxime Coquelin <maxime.coquelin@...hat.com>, mst@...hat.com,
jasowang@...hat.com, xuanzhuo@...ux.alibaba.com,
paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com,
stephen.smalley.work@...il.com, eparis@...isplace.org,
xieyongji@...edance.com, virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
david.marchand@...hat.com, lulu@...hat.com,
Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v4 4/4] vduse: Add LSM hooks to check Virtio device type
On 10/20/2023 8:58 AM, Maxime Coquelin wrote:
> This patch introduces LSM hooks for devices creation,
> destruction and opening operations, checking the
> application is allowed to perform these operations for
> the Virtio device type.
Why do you think that there needs to be a special LSM check for virtio
devices? What can't existing device attributes be used?
>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@...hat.com>
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 12 +++++++
> include/linux/lsm_hook_defs.h | 4 +++
> include/linux/security.h | 15 ++++++++
> security/security.c | 42 ++++++++++++++++++++++
> security/selinux/hooks.c | 55 +++++++++++++++++++++++++++++
> security/selinux/include/classmap.h | 2 ++
> 6 files changed, 130 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 0243dee9cf0e..ca64eac11ddb 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -8,6 +8,7 @@
> *
> */
>
> +#include "linux/security.h"
> #include <linux/init.h>
> #include <linux/module.h>
> #include <linux/cdev.h>
> @@ -1443,6 +1444,10 @@ static int vduse_dev_open(struct inode *inode, struct file *file)
> if (dev->connected)
> goto unlock;
>
> + ret = -EPERM;
> + if (security_vduse_dev_open(dev->device_id))
> + goto unlock;
> +
> ret = 0;
> dev->connected = true;
> file->private_data = dev;
> @@ -1655,6 +1660,9 @@ static int vduse_destroy_dev(char *name)
> if (!dev)
> return -EINVAL;
>
> + if (security_vduse_dev_destroy(dev->device_id))
> + return -EPERM;
> +
> mutex_lock(&dev->lock);
> if (dev->vdev || dev->connected) {
> mutex_unlock(&dev->lock);
> @@ -1819,6 +1827,10 @@ static int vduse_create_dev(struct vduse_dev_config *config,
> int ret;
> struct vduse_dev *dev;
>
> + ret = -EPERM;
> + if (security_vduse_dev_create(config->device_id))
> + goto err;
> +
> ret = -EEXIST;
> if (vduse_find_dev(config->name))
> goto err;
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index ac962c4cb44b..0b3999ab3264 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -419,3 +419,7 @@ LSM_HOOK(int, 0, uring_override_creds, const struct cred *new)
> LSM_HOOK(int, 0, uring_sqpoll, void)
> LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd)
> #endif /* CONFIG_IO_URING */
> +
> +LSM_HOOK(int, 0, vduse_dev_create, u32 device_id)
> +LSM_HOOK(int, 0, vduse_dev_destroy, u32 device_id)
> +LSM_HOOK(int, 0, vduse_dev_open, u32 device_id)
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 5f16eecde00b..a650c500f841 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -484,6 +484,9 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
> int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
> int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
> int security_locked_down(enum lockdown_reason what);
> +int security_vduse_dev_create(u32 device_id);
> +int security_vduse_dev_destroy(u32 device_id);
> +int security_vduse_dev_open(u32 device_id);
> #else /* CONFIG_SECURITY */
>
> static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
> @@ -1395,6 +1398,18 @@ static inline int security_locked_down(enum lockdown_reason what)
> {
> return 0;
> }
> +static inline int security_vduse_dev_create(u32 device_id)
> +{
> + return 0;
> +}
> +static inline int security_vduse_dev_destroy(u32 device_id)
> +{
> + return 0;
> +}
> +static inline int security_vduse_dev_open(u32 device_id)
> +{
> + return 0;
> +}
> #endif /* CONFIG_SECURITY */
>
> #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
> diff --git a/security/security.c b/security/security.c
> index 23b129d482a7..8d7d4d2eca0b 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -5337,3 +5337,45 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd)
> return call_int_hook(uring_cmd, 0, ioucmd);
> }
> #endif /* CONFIG_IO_URING */
> +
> +/**
> + * security_vduse_dev_create() - Check if a VDUSE device type creation is allowed
> + * @device_id: the Virtio device ID
> + *
> + * Check whether the Virtio device creation is allowed
> + *
> + * Return: Returns 0 if permission is granted.
> + */
> +int security_vduse_dev_create(u32 device_id)
> +{
> + return call_int_hook(vduse_dev_create, 0, device_id);
> +}
> +EXPORT_SYMBOL(security_vduse_dev_create);
> +
> +/**
> + * security_vduse_dev_destroy() - Check if a VDUSE device type destruction is allowed
> + * @device_id: the Virtio device ID
> + *
> + * Check whether the Virtio device destruction is allowed
> + *
> + * Return: Returns 0 if permission is granted.
> + */
> +int security_vduse_dev_destroy(u32 device_id)
> +{
> + return call_int_hook(vduse_dev_destroy, 0, device_id);
> +}
> +EXPORT_SYMBOL(security_vduse_dev_destroy);
> +
> +/**
> + * security_vduse_dev_open() - Check if a VDUSE device type opening is allowed
> + * @device_id: the Virtio device ID
> + *
> + * Check whether the Virtio device opening is allowed
> + *
> + * Return: Returns 0 if permission is granted.
> + */
> +int security_vduse_dev_open(u32 device_id)
> +{
> + return call_int_hook(vduse_dev_open, 0, device_id);
> +}
> +EXPORT_SYMBOL(security_vduse_dev_open);
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 2aa0e219d721..65d9262a37f7 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -21,6 +21,7 @@
> * Copyright (C) 2016 Mellanox Technologies
> */
>
> +#include "av_permissions.h"
> #include <linux/init.h>
> #include <linux/kd.h>
> #include <linux/kernel.h>
> @@ -92,6 +93,7 @@
> #include <linux/fsnotify.h>
> #include <linux/fanotify.h>
> #include <linux/io_uring.h>
> +#include <uapi/linux/virtio_ids.h>
>
> #include "avc.h"
> #include "objsec.h"
> @@ -6950,6 +6952,56 @@ static int selinux_uring_cmd(struct io_uring_cmd *ioucmd)
> }
> #endif /* CONFIG_IO_URING */
>
> +static int vduse_check_device_type(u32 sid, u32 device_id)
> +{
> + u32 requested;
> +
> + if (device_id == VIRTIO_ID_NET)
> + requested = VDUSE__NET;
> + else if (device_id == VIRTIO_ID_BLOCK)
> + requested = VDUSE__BLOCK;
> + else
> + return -EINVAL;
> +
> + return avc_has_perm(sid, sid, SECCLASS_VDUSE, requested, NULL);
> +}
> +
> +static int selinux_vduse_dev_create(u32 device_id)
> +{
> + u32 sid = current_sid();
> + int ret;
> +
> + ret = avc_has_perm(sid, sid, SECCLASS_VDUSE, VDUSE__DEVCREATE, NULL);
> + if (ret)
> + return ret;
> +
> + return vduse_check_device_type(sid, device_id);
> +}
> +
> +static int selinux_vduse_dev_destroy(u32 device_id)
> +{
> + u32 sid = current_sid();
> + int ret;
> +
> + ret = avc_has_perm(sid, sid, SECCLASS_VDUSE, VDUSE__DEVDESTROY, NULL);
> + if (ret)
> + return ret;
> +
> + return vduse_check_device_type(sid, device_id);
> +}
> +
> +static int selinux_vduse_dev_open(u32 device_id)
> +{
> + u32 sid = current_sid();
> + int ret;
> +
> + ret = avc_has_perm(sid, sid, SECCLASS_VDUSE, VDUSE__DEVOPEN, NULL);
> + if (ret)
> + return ret;
> +
> + return vduse_check_device_type(sid, device_id);
> +}
> +
> /*
> * IMPORTANT NOTE: When adding new hooks, please be careful to keep this order:
> * 1. any hooks that don't belong to (2.) or (3.) below,
> @@ -7243,6 +7295,9 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
> #ifdef CONFIG_PERF_EVENTS
> LSM_HOOK_INIT(perf_event_alloc, selinux_perf_event_alloc),
> #endif
> + LSM_HOOK_INIT(vduse_dev_create, selinux_vduse_dev_create),
> + LSM_HOOK_INIT(vduse_dev_destroy, selinux_vduse_dev_destroy),
> + LSM_HOOK_INIT(vduse_dev_open, selinux_vduse_dev_open),
> };
>
> static __init int selinux_init(void)
> diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
> index a3c380775d41..d3dc37fb03d4 100644
> --- a/security/selinux/include/classmap.h
> +++ b/security/selinux/include/classmap.h
> @@ -256,6 +256,8 @@ const struct security_class_mapping secclass_map[] = {
> { "override_creds", "sqpoll", "cmd", NULL } },
> { "user_namespace",
> { "create", NULL } },
> + { "vduse",
> + { "devcreate", "devdestroy", "devopen", "net", "block", NULL} },
> { NULL }
> };
>
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