From: Catalin Marinas <catalin.marinas@xxxxxxx>
Subject: 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@xxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reported-by: CAI Qian <caiqian@xxxxxxxxxx>
Tested-by: CAI Qian <caiqian@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: CAI Qian <caiqian@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kmemleak.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff -puN mm/kmemleak.c~mm-kmemleak-ensure-that-the-task-stack-is-not-freed-during-scanning mm/kmemleak.c
--- a/mm/kmemleak.c~mm-kmemleak-ensure-that-the-task-stack-is-not-freed-during-scanning
+++ a/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);
}
_
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