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Commit 6d2661ed authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

oom: fix possible oom_dump_tasks NULL pointer 



When /proc/sys/vm/oom_dump_tasks is enabled, it is possible to get a NULL
pointer for tasks that have detached mm's since task_lock() is not held
during the tasklist scan.  Add the task_lock().

Acked-by: default avatarNick Piggin <npiggin@suse.de>
Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 681a1b40

mm/oom_kill.c

+15 −9
Original line number Diff line number Diff line
@@ -284,22 +284,28 @@ static void dump_tasks(const struct mem_cgroup *mem) 
	printk(KERN_INFO "[ pid ]   uid  tgid total_vm      rss cpu oom_adj "

	       "name\n");

	do_each_thread(g, p) {

		/*

		 * total_vm and rss sizes do not exist for tasks with a

		 * detached mm so there's no need to report them.

		 */

		if (!p->mm)

			continue;

		struct mm_struct *mm;



		if (mem && !task_in_mem_cgroup(p, mem))

			continue;

		if (!thread_group_leader(p))

			continue;



		task_lock(p);

		mm = p->mm;

		if (!mm) {

			/*

			 * total_vm and rss sizes do not exist for tasks with no

			 * mm so there's no need to report them; they can't be

			 * oom killed anyway.

			 */

			task_unlock(p);

			continue;

		}

		printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d     %3d %s\n",

		       p->pid, __task_cred(p)->uid, p->tgid,

		       p->mm->total_vm, get_mm_rss(p->mm), (int)task_cpu(p),

		       p->oomkilladj, p->comm);

		       p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm,

		       get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj,

		       p->comm);

		task_unlock(p);

	} while_each_thread(g, p);

}