Messages in this thread Patch in this message | | | Date | Thu, 1 Apr 2010 15:13:57 +0200 | From | Oleg Nesterov <> | Subject | [PATCH 1/1] oom: fix the unsafe usage of badness() in proc_oom_score() |
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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.
- 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> ---
fs/proc/base.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- TTT/fs/proc/base.c~PROC_OOM_SCORE 2010-03-11 13:11:50.000000000 +0100 +++ TTT/fs/proc/base.c 2010-04-01 14:41:17.000000000 +0200 @@ -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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