From dd9037a26a1e6ebec9121b4681c414dc77189a90 Mon Sep 17 00:00:00 2001 From: Srivatsa Vaddagiri Date: Tue, 8 May 2007 00:27:25 -0700 Subject: [PATCH] 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: Srivatsa Vaddagiri Cc: Paul Jackson Cc: Balbir Singh Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/cpuset.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index d240349cbf0f..bde714db2b26 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -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;