[PATCH] oom: fix the unsafe proc_oom_score()->badness() call
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From: Oleg Nesterov on 30 Mar 2010 12:50 proc_oom_score(task) have 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. Add the pid_alive() check to ensure __unhash_process() was not called. Note: I think we shouldn't use ->group_leader, badness() should return the same result for any sub-thread. However this is not true currently, and I think that ->mm check and list_for_each_entry(p->children) in badness are not right. Signed-off-by: Oleg Nesterov <oleg(a)redhat.com> --- fs/proc/base.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- 34-rc1/fs/proc/base.c~OOM_SCORE 2010-03-22 16:36:28.000000000 +0100 +++ 34-rc1/fs/proc/base.c 2010-03-30 18:23:50.000000000 +0200 @@ -430,12 +430,13 @@ 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->group_leader, uptime.tv_sec); read_unlock(&tasklist_lock); return sprintf(buffer, "%lu\n", points); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |