| Date | Thu, 22 Apr 2010 12:53:02 -0700 | From | Greg KH <> | Subject | [005/139] oom: fix the unsafe usage of badness() in proc_oom_score() |
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2.6.33-stable review patch. If anyone has any objections, please let us know.
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From: Oleg Nesterov <oleg@redhat.com>
commit b95c35e76b29ba812e5dabdd91592e25ec640e93 upstream.
proc_oom_score(task) has a reference to task_struct, but that is all. If this task was already released before we take tasklist_lock
- we can't use task->group_leader, it points to nowhere
- it is not safe to call badness() even if this task is ->group_leader, has_intersects_mems_allowed() assumes it is safe to iterate over ->thread_group list.
- even worse, badness() can hit ->signal == NULL
Add the pid_alive() check to ensure __unhash_process() was not called.
Also, use "task" instead of task->group_leader. badness() should return the same result for any sub-thread. Currently this is not true, but this should be changed anyway.
Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- fs/proc/base.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -442,12 +442,13 @@ static const struct file_operations proc unsigned long badness(struct task_struct *p, unsigned long uptime); static int proc_oom_score(struct task_struct *task, char *buffer) { - unsigned long points; + unsigned long points = 0; struct timespec uptime; do_posix_clock_monotonic_gettime(&uptime); read_lock(&tasklist_lock); - points = badness(task->group_leader, uptime.tv_sec); + if (pid_alive(task)) + points = badness(task, uptime.tv_sec); read_unlock(&tasklist_lock); return sprintf(buffer, "%lu\n", points); }
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