diff mbox

[RFC,2/2,v2] security: Add task_settimerslack LSM hook

Message ID 1468603460-17034-2-git-send-email-john.stultz@linaro.org
State New
Headers show

Commit Message

John Stultz July 15, 2016, 5:24 p.m. UTC 
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@chromium.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
CC: Arjan van de Ven <arjan@linux.intel.com>
Cc: Oren Laadan <orenl@cellrox.com>
Cc: Ruchi Kandoi <kandoiruchi@google.com>
Cc: Rom Lemarchand <romlem@android.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Colin Cross <ccross@android.com>
Cc: Nick Kralevich <nnk@google.com>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: Elliott Hughes <enh@google.com>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.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(+)

-- 
1.9.1

Comments

John Stultz July 15, 2016, 6:10 p.m. UTC | #1 
On Fri, Jul 15, 2016 at 10:51 AM, Nick Kralevich <nnk@google.com> wrote:
> On Fri, Jul 15, 2016 at 10:24 AM, John Stultz <john.stultz@linaro.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@chromium.org>

>> Cc: "Serge E. Hallyn" <serge@hallyn.com>

>> Cc: Andrew Morton <akpm@linux-foundation.org>

>> Cc: Thomas Gleixner <tglx@linutronix.de>

>> CC: Arjan van de Ven <arjan@linux.intel.com>

>> Cc: Oren Laadan <orenl@cellrox.com>

>> Cc: Ruchi Kandoi <kandoiruchi@google.com>

>> Cc: Rom Lemarchand <romlem@android.com>

>> Cc: Todd Kjos <tkjos@google.com>

>> Cc: Colin Cross <ccross@android.com>

>> Cc: Nick Kralevich <nnk@google.com>

>> Cc: Dmitry Shmidt <dimitrysh@google.com>

>> Cc: Elliott Hughes <enh@google.com>

>> Cc: Android Kernel Team <kernel-team@android.com>

>> Signed-off-by: John Stultz <john.stultz@linaro.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.


Ah, yes. Thanks. Clearly I don't know what I'm doing here. :)
-john
diff mbox

Patch

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);
+	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),