From 37df49f433bc3a11f5716fe65aaec5189c6402cb Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Thu, 27 Oct 2016 17:46:47 -0700 Subject: [PATCH] mm: kmemleak: ensure that the task stack is not freed during scanning 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 Reported-by: CAI Qian Tested-by: CAI Qian Acked-by: Michal Hocko Cc: Andy Lutomirski Cc: CAI Qian Cc: Hillf Danton Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/kmemleak.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index a5e453cf05c4..e5355a5b423f 100644 --- 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); }