Messages in this thread Patch in this message | | | From | Catalin Marinas <> | Subject | [PATCH] mm: kmemleak: Ensure that the task stack is not freed during scanning | Date | Wed, 12 Oct 2016 10:57:03 +0100 |
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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@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: CAI Qian <caiqian@redhat.com> Reported-by: CAI Qian <caiqian@redhat.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> ---
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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