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authorDhaval Giani <dhaval@linux.vnet.ibm.com>2009-02-27 04:43:54 -0500
committerIngo Molnar <mingo@elte.hu>2009-02-27 05:11:53 -0500
commit54e991242850edc8c53f71fa5aa3ba7a93ce38f5 (patch)
tree7f136214aab690a8ee4a294ca9c1a7e01de0dc49
parentcac64d00c256e65776d575e82aaf540632b66178 (diff)
sched: don't allow setuid to succeed if the user does not have rt bandwidth
Impact: fix hung task with certain (non-default) rt-limit settings Corey Hickey reported that on using setuid to change the uid of a rt process, the process would be unkillable and not be running. This is because there was no rt runtime for that user group. Add in a check to see if a user can attach an rt task to its task group. On failure, return EINVAL, which is also returned in CONFIG_CGROUP_SCHED. Reported-by: Corey Hickey <bugfood-ml@fatooh.org> Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--include/linux/sched.h4
-rw-r--r--kernel/sched.c13
-rw-r--r--kernel/sys.c31
-rw-r--r--kernel/user.c18
4 files changed, 53 insertions, 13 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8981e52c714f..8c216e057c94 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2291,9 +2291,13 @@ extern long sched_group_rt_runtime(struct task_group *tg);
2291extern int sched_group_set_rt_period(struct task_group *tg, 2291extern int sched_group_set_rt_period(struct task_group *tg,
2292 long rt_period_us); 2292 long rt_period_us);
2293extern long sched_group_rt_period(struct task_group *tg); 2293extern long sched_group_rt_period(struct task_group *tg);
2294extern int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk);
2294#endif 2295#endif
2295#endif 2296#endif
2296 2297
2298extern int task_can_switch_user(struct user_struct *up,
2299 struct task_struct *tsk);
2300
2297#ifdef CONFIG_TASK_XACCT 2301#ifdef CONFIG_TASK_XACCT
2298static inline void add_rchar(struct task_struct *tsk, ssize_t amt) 2302static inline void add_rchar(struct task_struct *tsk, ssize_t amt)
2299{ 2303{
diff --git a/kernel/sched.c b/kernel/sched.c
index c3baa9653d1d..8e2558c2ba67 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -9224,6 +9224,16 @@ static int sched_rt_global_constraints(void)
9224 9224
9225 return ret; 9225 return ret;
9226} 9226}
9227
9228int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
9229{
9230 /* Don't accept realtime tasks when there is no way for them to run */
9231 if (rt_task(tsk) && tg->rt_bandwidth.rt_runtime == 0)
9232 return 0;
9233
9234 return 1;
9235}
9236
9227#else /* !CONFIG_RT_GROUP_SCHED */ 9237#else /* !CONFIG_RT_GROUP_SCHED */
9228static int sched_rt_global_constraints(void) 9238static int sched_rt_global_constraints(void)
9229{ 9239{
@@ -9317,8 +9327,7 @@ cpu_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
9317 struct task_struct *tsk) 9327 struct task_struct *tsk)
9318{ 9328{
9319#ifdef CONFIG_RT_GROUP_SCHED 9329#ifdef CONFIG_RT_GROUP_SCHED
9320 /* Don't accept realtime tasks when there is no way for them to run */ 9330 if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
9321 if (rt_task(tsk) && cgroup_tg(cgrp)->rt_bandwidth.rt_runtime == 0)
9322 return -EINVAL; 9331 return -EINVAL;
9323#else 9332#else
9324 /* We don't support RT-tasks being in separate groups */ 9333 /* We don't support RT-tasks being in separate groups */
diff --git a/kernel/sys.c b/kernel/sys.c
index f145c415bc16..37f458e6882a 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -559,7 +559,7 @@ error:
559 abort_creds(new); 559 abort_creds(new);
560 return retval; 560 return retval;
561} 561}
562 562
563/* 563/*
564 * change the user struct in a credentials set to match the new UID 564 * change the user struct in a credentials set to match the new UID
565 */ 565 */
@@ -571,6 +571,11 @@ static int set_user(struct cred *new)
571 if (!new_user) 571 if (!new_user)
572 return -EAGAIN; 572 return -EAGAIN;
573 573
574 if (!task_can_switch_user(new_user, current)) {
575 free_uid(new_user);
576 return -EINVAL;
577 }
578
574 if (atomic_read(&new_user->processes) >= 579 if (atomic_read(&new_user->processes) >=
575 current->signal->rlim[RLIMIT_NPROC].rlim_cur && 580 current->signal->rlim[RLIMIT_NPROC].rlim_cur &&
576 new_user != INIT_USER) { 581 new_user != INIT_USER) {
@@ -631,10 +636,11 @@ SYSCALL_DEFINE2(setreuid, uid_t, ruid, uid_t, euid)
631 goto error; 636 goto error;
632 } 637 }
633 638
634 retval = -EAGAIN; 639 if (new->uid != old->uid) {
635 if (new->uid != old->uid && set_user(new) < 0) 640 retval = set_user(new);
636 goto error; 641 if (retval < 0)
637 642 goto error;
643 }
638 if (ruid != (uid_t) -1 || 644 if (ruid != (uid_t) -1 ||
639 (euid != (uid_t) -1 && euid != old->uid)) 645 (euid != (uid_t) -1 && euid != old->uid))
640 new->suid = new->euid; 646 new->suid = new->euid;
@@ -680,9 +686,10 @@ SYSCALL_DEFINE1(setuid, uid_t, uid)
680 retval = -EPERM; 686 retval = -EPERM;
681 if (capable(CAP_SETUID)) { 687 if (capable(CAP_SETUID)) {
682 new->suid = new->uid = uid; 688 new->suid = new->uid = uid;
683 if (uid != old->uid && set_user(new) < 0) { 689 if (uid != old->uid) {
684 retval = -EAGAIN; 690 retval = set_user(new);
685 goto error; 691 if (retval < 0)
692 goto error;
686 } 693 }
687 } else if (uid != old->uid && uid != new->suid) { 694 } else if (uid != old->uid && uid != new->suid) {
688 goto error; 695 goto error;
@@ -734,11 +741,13 @@ SYSCALL_DEFINE3(setresuid, uid_t, ruid, uid_t, euid, uid_t, suid)
734 goto error; 741 goto error;
735 } 742 }
736 743
737 retval = -EAGAIN;
738 if (ruid != (uid_t) -1) { 744 if (ruid != (uid_t) -1) {
739 new->uid = ruid; 745 new->uid = ruid;
740 if (ruid != old->uid && set_user(new) < 0) 746 if (ruid != old->uid) {
741 goto error; 747 retval = set_user(new);
748 if (retval < 0)
749 goto error;
750 }
742 } 751 }
743 if (euid != (uid_t) -1) 752 if (euid != (uid_t) -1)
744 new->euid = euid; 753 new->euid = euid;
diff --git a/kernel/user.c b/kernel/user.c
index 3551ac742395..6a9b696128c8 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -362,6 +362,24 @@ static void free_user(struct user_struct *up, unsigned long flags)
362 362
363#endif 363#endif
364 364
365#if defined(CONFIG_RT_GROUP_SCHED) && defined(CONFIG_USER_SCHED)
366/*
367 * We need to check if a setuid can take place. This function should be called
368 * before successfully completing the setuid.
369 */
370int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
371{
372
373 return sched_rt_can_attach(up->tg, tsk);
374
375}
376#else
377int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
378{
379 return 1;
380}
381#endif
382
365/* 383/*
366 * Locate the user_struct for the passed UID. If found, take a ref on it. The 384 * Locate the user_struct for the passed UID. If found, take a ref on it. The
367 * caller must undo that ref with free_uid(). 385 * caller must undo that ref with free_uid().