On Tue, 7 Nov 2017 09:57:03 -0800 Shaohua Li <s...@fb.com> wrote:
> kthread() could bail out early before we initialize blkcg_css (if the
> kthread is killed very soon), which confuses free_kthread_struct. Move
> the blkcg_css initialization early.
Changelog is... minimal. I guess it doesn't matter much.
> Reported-by: syzbot <syzkal...@googlegroups.com>
> Fix: 05e3db9(kthread: add a mechanism to store cgroup info)
That's a bit messed up. Please use
Fixes: 05e3db95ebfc ("kthread: add a mechanism to store cgroup info")
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -205,6 +205,10 @@ static int kthread(void *_create)
> int ret;
>
> self = kmalloc(sizeof(*self), GFP_KERNEL);
> +#ifdef CONFIG_BLK_CGROUP
> + if (self)
> + self->blkcg_css = NULL;
> +#endif
Using kzalloc() would be much neater. That way we get to delete a bit
more code and it doesn't leave me wondering "under what circumstances
is kthread.cpu uninitialized". At least, not as much as I am wondering
right now.
