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Commit dd9037a2 authored by Srivatsa Vaddagiri's avatar Srivatsa Vaddagiri Committed by Linus Torvalds
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Fix race between attach_task and cpuset_exit 

Currently cpuset_exit() changes the exiting task's ->cpuset pointer w/o
taking task_lock().  This can lead to ugly races between attach_task and
cpuset_exit.  Details of the races are described at
http://lkml.org/lkml/2007/3/24/132

.

Patch below closes those races.

Signed-off-by: default avatarSrivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e5f00f42

kernel/cpuset.c

+2 −4
Original line number Diff line number Diff line
@@ -2200,10 +2200,6 @@ void cpuset_fork(struct task_struct *child) 
 * it is holding that mutex while calling check_for_release(),

 * which calls kmalloc(), so can't be called holding callback_mutex().

 *

 * We don't need to task_lock() this reference to tsk->cpuset,

 * because tsk is already marked PF_EXITING, so attach_task() won't

 * mess with it, or task is a failed fork, never visible to attach_task.

 *

 * the_top_cpuset_hack:

 *

 *    Set the exiting tasks cpuset to the root cpuset (top_cpuset).
@@ -2242,8 +2238,10 @@ void cpuset_exit(struct task_struct *tsk) 
{

	struct cpuset *cs;



	task_lock(current);

	cs = tsk->cpuset;

	tsk->cpuset = &top_cpuset;	/* the_top_cpuset_hack - see above */

	task_unlock(current);



	if (notify_on_release(cs)) {

		char *pathbuf = NULL;