Re: [PATCH] workqueue: fix null-ptr-deref on __alloc_workqueue() error

From: Matthew Brost
Date: Thu Aug 15 2024 - 11:57:57 EST


On Thu, Aug 15, 2024 at 04:24:27PM +0900, Sergey Senozhatsky wrote:
> On (24/08/15 16:09), Sergey Senozhatsky wrote:
> > On (24/08/15 16:02), Sergey Senozhatsky wrote:
> > Oh, okay, so this is related to [1]
> >
> > workqueue: Split alloc_workqueue into internal function and lockdep init
> >
> > Cc-ing Matthew on this.
> >
> > [1] https://lore.kernel.org/all/20240809222827.3211998-2-matthew.brost@xxxxxxxxx/
>
> Matthew, did you mean to do something like below instead?
> Otherwise it breaks boot for me.
>

Yikes, my bad. My change worked locally and in Intel's CI for Xe [2]. So
I did not realize this was an issue the way I had it coded.

I believe you when you say this is an issue.

With that, the way I coded alloc_ordered_workqueue_lockdep_map could
also be dangerous. Thinking that also should also be changed back to a
macro too.

Let's see what Tejon thinks?

Matt

[2] https://patchwork.freedesktop.org/series/136701/

> ---
>
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 7a2f4cbbe8b2..55e0e69ee604 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -5615,12 +5615,11 @@ static void wq_adjust_max_active(struct workqueue_struct *wq)
> } while (activated);
> }
>
> -__printf(1, 4)
> static struct workqueue_struct *__alloc_workqueue(const char *fmt,
> unsigned int flags,
> - int max_active, ...)
> + int max_active,
> + va_list args)
> {
> - va_list args;
> struct workqueue_struct *wq;
> size_t wq_size;
> int name_len;
> @@ -5652,9 +5651,7 @@ static struct workqueue_struct *__alloc_workqueue(const char *fmt,
> goto err_free_wq;
> }
>
> - va_start(args, max_active);
> name_len = vsnprintf(wq->name, sizeof(wq->name), fmt, args);
> - va_end(args);
>
> if (name_len >= WQ_NAME_LEN)
> pr_warn_once("workqueue: name exceeds WQ_NAME_LEN. Truncating to: %s\n",