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.
Fixes: 68f24b08ee89 ("sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK")
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: CAI Qian <caiqian@xxxxxxxxxx>
Reported-by: CAI Qian <caiqian@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
---
This was reported in a subsequent comment here:
https://bugzilla.kernel.org/show_bug.cgi?id=173901
However, the original bugzilla entry doesn't look related to task stack
freeing as it was first reported on 4.8-rc8. Andy, sorry for cc'ing you
to bugzilla, please feel free to remove your email from the bug above (I
can't seem to be able to do it).
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);
}
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