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sched: don't allow setuid to succeed if the user does not have rt bandwidth

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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>
This commit is contained in:
Dhaval Giani
2009-02-27 15:13:54 +05:30
committed by Ingo Molnar
parent cac64d00c2
commit 54e9912428
4 changed files with 53 additions and 13 deletions
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18
kernel/user.c
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@@ -362,6 +362,24 @@ static void free_user(struct user_struct *up, unsigned long flags)
#endif
#if defined(CONFIG_RT_GROUP_SCHED) && defined(CONFIG_USER_SCHED)
/*
* We need to check if a setuid can take place. This function should be called
* before successfully completing the setuid.
*/
int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
{
return sched_rt_can_attach(up->tg, tsk);
}
#else
int task_can_switch_user(struct user_struct *up, struct task_struct *tsk)
{
return 1;
}
#endif
/*
* Locate the user_struct for the passed UID. If found, take a ref on it. The
* caller must undo that ref with free_uid().