[PATCH] lsm: add task_setioprio hook

Implement an LSM hook for setting a task's IO priority, similar to the hook
for setting a tasks's nice value.

A previous version of this LSM hook was included in an older version of
multiadm by Jan Engelhardt, although I don't recall it being submitted
upstream.

Also included is the corresponding SELinux hook, which re-uses the setsched
permission in the proccess class.

Signed-off-by: James Morris <jmorris@namei.org>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

security/dummy.c

diff --git a/security/dummy.c b/security/dummy.c
index c98d553..879a985 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -516,6 +516,11 @@
 	return 0;
 }
 
+static int dummy_task_setioprio (struct task_struct *p, int ioprio)
+{
+	return 0;
+}
+
 static int dummy_task_setrlimit (unsigned int resource, struct rlimit *new_rlim)
 {
 	return 0;
@@ -972,6 +977,7 @@
 	set_to_dummy_if_null(ops, task_getsid);
 	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_setrlimit);
 	set_to_dummy_if_null(ops, task_setscheduler);
 	set_to_dummy_if_null(ops, task_getscheduler);

security/selinux/hooks.c

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 093efba..9dcf298 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2645,6 +2645,11 @@
 	return task_has_perm(current,p, PROCESS__SETSCHED);
 }
 
+static int selinux_task_setioprio(struct task_struct *p, int ioprio)
+{
+	return task_has_perm(current, p, PROCESS__SETSCHED);
+}
+
 static int selinux_task_setrlimit(unsigned int resource, struct rlimit *new_rlim)
 {
 	struct rlimit *old_rlim = current->signal->rlim + resource;
@@ -4383,6 +4388,7 @@
 	.task_getsid =		        selinux_task_getsid,
 	.task_setgroups =		selinux_task_setgroups,
 	.task_setnice =			selinux_task_setnice,
+	.task_setioprio =		selinux_task_setioprio,
 	.task_setrlimit =		selinux_task_setrlimit,
 	.task_setscheduler =		selinux_task_setscheduler,
 	.task_getscheduler =		selinux_task_getscheduler,