mm: kmemleak: ensure that the task stack is not freed during scanning
authorCatalin Marinas <catalin.marinas@arm.com>
Fri, 28 Oct 2016 00:46:47 +0000 (17:46 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 28 Oct 2016 01:43:43 +0000 (18:43 -0700)
Commit 68f24b08ee89 ("sched/core: Free the stack early if
CONFIG_THREAD_INFO_IN_TASK") may cause the task->stack to be freed
during kmemleak_scan() execution, leading to either a NULL pointer fault
(if task->stack is NULL) or kmemleak accessing already freed memory.

This patch uses the new try_get_task_stack() API to ensure that the task
stack is not freed during kmemleak stack scanning.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=173901.

Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK")
Link: http://lkml.kernel.org/r/1476266223-14325-1-git-send-email-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: CAI Qian <caiqian@redhat.com>
Tested-by: CAI Qian <caiqian@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: CAI Qian <caiqian@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/kmemleak.c

index a5e453cf05c499cf5c7eeb9b66ce14936d4494fd..e5355a5b423fa9fd61a77ebf7b94819ec2e199df 100644 (file)
@@ -1453,8 +1453,11 @@ static void kmemleak_scan(void)
 
                read_lock(&tasklist_lock);
                do_each_thread(g, p) {
-                       scan_block(task_stack_page(p), task_stack_page(p) +
-                                  THREAD_SIZE, NULL);
+                       void *stack = try_get_task_stack(p);
+                       if (stack) {
+                               scan_block(stack, stack + THREAD_SIZE, NULL);
+                               put_task_stack(p);
+                       }
                } while_each_thread(g, p);
                read_unlock(&tasklist_lock);
        }