Re: [PATCH] oom: fix the unsafe proc_oom_score()->badness() call
From: David Rientjes
Date: Thu Apr 01 2010 - 03:42:04 EST
On Wed, 31 Mar 2010, Oleg Nesterov wrote:
> But. Oh well. David, oom-badness-heuristic-rewrite.patch changed badness()
> to consult p->signal->oom_score_adj. Until recently this was wrong when it
> is called from proc_oom_score().
> This means oom-badness-heuristic-rewrite.patch depends on
> signals-make-task_struct-signal-immutable-refcountable.patch, or we
> need the pid_alive() check again.
oom-badness-heuristic-rewrite.patch didn't change anything, Linus' tree
currently dereferences p->signal->oom_adj which is no different from
dereferencing p->signal->oom_score_adj without a refcount on the
signal_struct in -mm. oom_adj was moved to struct signal_struct in
2.6.32, see 28b83c5.
> oom_badness() gets the new argument, long totalpages, and the callers
> were updated. However, long uptime is not used any longer, probably
> it make sense to kill this arg and simplify the callers? Unless you
> are going to take run-time into account later.
> So, I think -mm needs the patch below, but I have no idea how to
> write the changelog ;)
> --- x/fs/proc/base.c
> +++ x/fs/proc/base.c
> @@ -430,12 +430,13 @@ static const struct file_operations proc
> /* The badness from the OOM killer */
> static int proc_oom_score(struct task_struct *task, char *buffer)
> - unsigned long points;
> + unsigned long points = 0;
> struct timespec uptime;
> - points = oom_badness(task->group_leader,
> + if (pid_alive(task))
> + points = oom_badness(task,
> global_page_state(NR_INACTIVE_ANON) +
> global_page_state(NR_ACTIVE_ANON) +
> global_page_state(NR_INACTIVE_FILE) +
This should be protected by the get_proc_task() on the inode before
this function is called from proc_info_read().
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/