[PATCH] SELinux: Add security hook definition for getioprio and insert hooks

Add a new security hook definition for the sys_ioprio_get operation.  At
present, the SELinux hook function implementation for this hook is
identical to the getscheduler implementation but a separate hook is
introduced to allow this check to be specialized in the future if
necessary.

This patch also creates a helper function get_task_ioprio which handles the
access check in addition to retrieving the ioprio value for the task.
Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/ioprio.c

@@ -125,11 +125,24 @@ asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
 	return ret;
 }
 
+static int get_task_ioprio(struct task_struct *p)
+{
+	int ret;
+
+	ret = security_task_getioprio(p);
+	if (ret)
+		goto out;
+	ret = p->ioprio;
+out:
+	return ret;
+}
+
 asmlinkage long sys_ioprio_get(int which, int who)
 {
 	struct task_struct *g, *p;
 	struct user_struct *user;
 	int ret = -ESRCH;
+	int tmpio;
 
 	read_lock_irq(&tasklist_lock);
 	switch (which) {
@@ -139,16 +152,19 @@ asmlinkage long sys_ioprio_get(int which, int who)
 			else
 				p = find_task_by_pid(who);
 			if (p)
-				ret = p->ioprio;
+				ret = get_task_ioprio(p);
 			break;
 		case IOPRIO_WHO_PGRP:
 			if (!who)
 				who = process_group(current);
 			do_each_task_pid(who, PIDTYPE_PGID, p) {
+				tmpio = get_task_ioprio(p);
+				if (tmpio < 0)
+					continue;
 				if (ret == -ESRCH)
-					ret = p->ioprio;
+					ret = tmpio;
 				else
-					ret = ioprio_best(ret, p->ioprio);
+					ret = ioprio_best(ret, tmpio);
 			} while_each_task_pid(who, PIDTYPE_PGID, p);
 			break;
 		case IOPRIO_WHO_USER:
@@ -163,10 +179,13 @@ asmlinkage long sys_ioprio_get(int which, int who)
 			do_each_thread(g, p) {
 				if (p->uid != user->uid)
 					continue;
+				tmpio = get_task_ioprio(p);
+				if (tmpio < 0)
+					continue;
 				if (ret == -ESRCH)
-					ret = p->ioprio;
+					ret = tmpio;
 				else
-					ret = ioprio_best(ret, p->ioprio);
+					ret = ioprio_best(ret, tmpio);
 			} while_each_thread(g, p);
 
 			if (who)

include/linux/security.h

@@ -585,6 +585,10 @@ struct swap_info_struct;
  *	@p contains the task_struct of process.
  *	@ioprio contains the new ioprio value
  *	Return 0 if permission is granted.
+ * @task_getioprio
+ *	Check permission before getting the ioprio value of @p.
+ *	@p contains the task_struct of process.
+ *	Return 0 if permission is granted.
  * @task_setrlimit:
  *	Check permission before setting the resource limits of the current
  *	process for @resource to @new_rlim.  The old resource limit values can
@@ -1227,6 +1231,7 @@ struct security_operations {
 	int (*task_setgroups) (struct group_info *group_info);
 	int (*task_setnice) (struct task_struct * p, int nice);
 	int (*task_setioprio) (struct task_struct * p, int ioprio);
+	int (*task_getioprio) (struct task_struct * p);
 	int (*task_setrlimit) (unsigned int resource, struct rlimit * new_rlim);
 	int (*task_setscheduler) (struct task_struct * p, int policy,
 				  struct sched_param * lp);
@@ -1864,6 +1869,11 @@ static inline int security_task_setioprio (struct task_struct *p, int ioprio)
 	return security_ops->task_setioprio (p, ioprio);
 }
 
+static inline int security_task_getioprio (struct task_struct *p)
+{
+	return security_ops->task_getioprio (p);
+}
+
 static inline int security_task_setrlimit (unsigned int resource,
 					   struct rlimit *new_rlim)
 {
@@ -2520,6 +2530,11 @@ static inline int security_task_setioprio (struct task_struct *p, int ioprio)
 	return 0;
 }
 
+static inline int security_task_getioprio (struct task_struct *p)
+{
+	return 0;
+}
+
 static inline int security_task_setrlimit (unsigned int resource,
 					   struct rlimit *new_rlim)
 {

security/dummy.c

@@ -524,6 +524,11 @@ static int dummy_task_setioprio (struct task_struct *p, int ioprio)
 	return 0;
 }
 
+static int dummy_task_getioprio (struct task_struct *p)
+{
+	return 0;
+}
+
 static int dummy_task_setrlimit (unsigned int resource, struct rlimit *new_rlim)
 {
 	return 0;
@@ -988,6 +993,7 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, task_setgroups);
 	set_to_dummy_if_null(ops, task_setnice);
 	set_to_dummy_if_null(ops, task_setioprio);
+	set_to_dummy_if_null(ops, task_getioprio);
 	set_to_dummy_if_null(ops, task_setrlimit);
 	set_to_dummy_if_null(ops, task_setscheduler);
 	set_to_dummy_if_null(ops, task_getscheduler);

security/selinux/hooks.c

@@ -2671,6 +2671,11 @@ static int selinux_task_setioprio(struct task_struct *p, int ioprio)
 	return task_has_perm(current, p, PROCESS__SETSCHED);
 }
 
+static int selinux_task_getioprio(struct task_struct *p)
+{
+	return task_has_perm(current, p, PROCESS__GETSCHED);
+}
+
 static int selinux_task_setrlimit(unsigned int resource, struct rlimit *new_rlim)
 {
 	struct rlimit *old_rlim = current->signal->rlim + resource;
@@ -4449,6 +4454,7 @@ static struct security_operations selinux_ops = {
 	.task_setgroups =		selinux_task_setgroups,
 	.task_setnice =			selinux_task_setnice,
 	.task_setioprio =		selinux_task_setioprio,
+	.task_getioprio =		selinux_task_getioprio,
 	.task_setrlimit =		selinux_task_setrlimit,
 	.task_setscheduler =		selinux_task_setscheduler,
 	.task_getscheduler =		selinux_task_getscheduler,