mm: kmemleak: ensure that the task stack is not freed during scanning

Commit 68f24b0 ("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: 68f24b0 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Catalin Marinas <[email protected]> Reported-by: CAI Qian <[email protected]> Tested-by: CAI Qian <[email protected]> Acked-by: Michal Hocko <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: CAI Qian <[email protected]> Cc: Hillf Danton <[email protected]> Cc: Oleg Nesterov <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
wafgo · Oct 28, 2016 · 37df49f · 37df49f
1 parent 02754e0
commit 37df49f
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
@@ -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);
 	}