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Date: Fri, 15 Jul 2016 10:51:25 -0700
From: Nick Kralevich <nnk@...gle.com>
To: John Stultz <john.stultz@...aro.org>
Cc: lkml <linux-kernel@...r.kernel.org>,
Kees Cook <keescook@...omium.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Arjan van de Ven <arjan@...ux.intel.com>,
Oren Laadan <orenl@...lrox.com>,
Ruchi Kandoi <kandoiruchi@...gle.com>,
Rom Lemarchand <romlem@...roid.com>,
Todd Kjos <tkjos@...gle.com>, Colin Cross <ccross@...roid.com>,
Dmitry Shmidt <dimitrysh@...gle.com>,
Elliott Hughes <enh@...gle.com>,
Android Kernel Team <kernel-team@...roid.com>,
linux-security-module@...r.kernel.org,
SELinux <selinux@...ho.nsa.gov>
Subject: Re: [RFC][PATCH 2/2 v2] security: Add task_settimerslack LSM hook
On Fri, Jul 15, 2016 at 10:24 AM, John Stultz <john.stultz@...aro.org> wrote:
> As requested, this patch implements a task_settimerslack LSM hook
> so that the /proc/<tid>/timerslack_ns interface can have finer
> grained security policies applied to it.
>
> Don't really know what I'm doing here, so close review would be
> appreciated!
>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: "Serge E. Hallyn" <serge@...lyn.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> CC: Arjan van de Ven <arjan@...ux.intel.com>
> Cc: Oren Laadan <orenl@...lrox.com>
> Cc: Ruchi Kandoi <kandoiruchi@...gle.com>
> Cc: Rom Lemarchand <romlem@...roid.com>
> Cc: Todd Kjos <tkjos@...gle.com>
> Cc: Colin Cross <ccross@...roid.com>
> Cc: Nick Kralevich <nnk@...gle.com>
> Cc: Dmitry Shmidt <dimitrysh@...gle.com>
> Cc: Elliott Hughes <enh@...gle.com>
> Cc: Android Kernel Team <kernel-team@...roid.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
> v2: Initial swing at adding LSM hook
>
> fs/proc/base.c | 7 +++++++
> include/linux/lsm_hooks.h | 7 +++++++
> include/linux/security.h | 6 ++++++
> security/security.c | 7 +++++++
> security/selinux/hooks.c | 6 ++++++
> 5 files changed, 33 insertions(+)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 8f4f8d7..7f10b37 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2284,6 +2284,12 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
> if (!p)
> return -ESRCH;
>
> + err = security_task_settimerslack(current, slack_ns);
The first argument should be "p", not "current". "p" is the target
process you're trying to adjust.
> + if (err) {
> + count = err;
> + goto out;
> + }
> +
> task_lock(p);
> if (slack_ns == 0)
> p->timer_slack_ns = p->default_timer_slack_ns;
> @@ -2291,6 +2297,7 @@ static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
> p->timer_slack_ns = slack_ns;
> task_unlock(p);
>
> +out:
> put_task_struct(p);
>
> return count;
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 7ae3976..ed546c4 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -627,6 +627,11 @@
> * Check permission before moving memory owned by process @p.
> * @p contains the task_struct for process.
> * Return 0 if permission is granted.
> + * @task_settimerslack:
> + * Check permission before setting timerslack value of @p to @slack.
> + * @p contains the task_struct of a process.
> + * @slack contains the new slack value.
> + * Return 0 if permission is granted.
> * @task_kill:
> * Check permission before sending signal @sig to @p. @info can be NULL,
> * the constant 1, or a pointer to a siginfo structure. If @info is 1 or
> @@ -1473,6 +1478,7 @@ union security_list_options {
> int (*task_setscheduler)(struct task_struct *p);
> int (*task_getscheduler)(struct task_struct *p);
> int (*task_movememory)(struct task_struct *p);
> + int (*task_settimerslack)(struct task_struct *p, u64 slack);
> int (*task_kill)(struct task_struct *p, struct siginfo *info,
> int sig, u32 secid);
> int (*task_wait)(struct task_struct *p);
> @@ -1732,6 +1738,7 @@ struct security_hook_heads {
> struct list_head task_setscheduler;
> struct list_head task_getscheduler;
> struct list_head task_movememory;
> + struct list_head task_settimerslack;
> struct list_head task_kill;
> struct list_head task_wait;
> struct list_head task_prctl;
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 14df373..1736e2b 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -325,6 +325,7 @@ int security_task_setrlimit(struct task_struct *p, unsigned int resource,
> int security_task_setscheduler(struct task_struct *p);
> int security_task_getscheduler(struct task_struct *p);
> int security_task_movememory(struct task_struct *p);
> +int security_task_settimerslack(struct task_struct *p, u64 slack);
> int security_task_kill(struct task_struct *p, struct siginfo *info,
> int sig, u32 secid);
> int security_task_wait(struct task_struct *p);
> @@ -950,6 +951,11 @@ static inline int security_task_movememory(struct task_struct *p)
> return 0;
> }
>
> +static inline int security_task_settimerslack(struct task_struct *p, u64 slack)
> +{
> + return 0;
> +}
> +
> static inline int security_task_kill(struct task_struct *p,
> struct siginfo *info, int sig,
> u32 secid)
> diff --git a/security/security.c b/security/security.c
> index 7095693..45f15cb 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -977,6 +977,11 @@ int security_task_movememory(struct task_struct *p)
> return call_int_hook(task_movememory, 0, p);
> }
>
> +int security_task_settimerslack(struct task_struct *p, u64 slack)
> +{
> + return call_int_hook(task_settimerslack, 0, p, slack);
> +}
> +
> int security_task_kill(struct task_struct *p, struct siginfo *info,
> int sig, u32 secid)
> {
> @@ -1720,6 +1725,8 @@ struct security_hook_heads security_hook_heads = {
> LIST_HEAD_INIT(security_hook_heads.task_getscheduler),
> .task_movememory =
> LIST_HEAD_INIT(security_hook_heads.task_movememory),
> + .task_settimerslack =
> + LIST_HEAD_INIT(security_hook_heads.task_settimerslack),
> .task_kill = LIST_HEAD_INIT(security_hook_heads.task_kill),
> .task_wait = LIST_HEAD_INIT(security_hook_heads.task_wait),
> .task_prctl = LIST_HEAD_INIT(security_hook_heads.task_prctl),
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index a86d537..e7c04322 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3849,6 +3849,11 @@ static int selinux_task_movememory(struct task_struct *p)
> return current_has_perm(p, PROCESS__SETSCHED);
> }
>
> +static int selinux_task_settimerslack(struct task_struct *p, u64 slack)
> +{
> + return current_has_perm(p, PROCESS__SETSCHED);
> +}
> +
> static int selinux_task_kill(struct task_struct *p, struct siginfo *info,
> int sig, u32 secid)
> {
> @@ -6092,6 +6097,7 @@ static struct security_hook_list selinux_hooks[] = {
> LSM_HOOK_INIT(task_setscheduler, selinux_task_setscheduler),
> LSM_HOOK_INIT(task_getscheduler, selinux_task_getscheduler),
> LSM_HOOK_INIT(task_movememory, selinux_task_movememory),
> + LSM_HOOK_INIT(task_settimerslack, selinux_task_settimerslack),
> LSM_HOOK_INIT(task_kill, selinux_task_kill),
> LSM_HOOK_INIT(task_wait, selinux_task_wait),
> LSM_HOOK_INIT(task_to_inode, selinux_task_to_inode),
> --
> 1.9.1
>
--
Nick Kralevich | Android Security | nnk@...gle.com | 650.214.4037
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