Re: [PATCH] workqueue: Fix incorrect error return value in apply_workqueue_attrs_locked

[Dan Carpenter <dan.carpenter@linaro.org>]

On Mon, Mar 24, 2025 at 05:07:48PM +0800, Ye Liu wrote:
v> From: Ye Liu <liuye@kylinos.cn>
> 
> Commit 84193c07105c ("workqueue: Generalize unbound CPU pods") introduced
> a change that caused apply_workqueue_attrs_locked() to return error
> pointers using PTR_ERR() on failure instead of a negative error code.

PTR_ERR() does return negative error codes.  Unless you pass it a NULL
pointer, then it returns success.  Or if you pass it a valid pointer it
returns garbage.

> This caused unexpected behavior in functions that rely on the return value
> of apply_workqueue_attrs_locked, such as alloc_and_link_pwqs().
> 
> Specifically, alloc_and_link_pwqs() expects apply_workqueue_attrs_locked()
> to return 0 on success and a negative error code on failure. However,
> returning PTR_ERR(ctx) instead of -ENOMEM led to incorrect error handling
> in __alloc_workqueue, potentially causing system instability or crashes.
> 
> This patch ensures apply_workqueue_attrs_locked() returns a proper negative
> error code (-ENOMEM) in case of failure, restoring expected behavior.
> 
> Fixes: 84193c07105c ("workqueue: Generalize unbound CPU pods")
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
>  kernel/workqueue.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index bfe030b443e2..8ba679d9b566 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -5363,7 +5363,7 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,
>  
>  	ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);
>  	if (IS_ERR(ctx))
> -		return PTR_ERR(ctx);
> +		return -ENOMEM;
>  

The original code was correct and the patch is wrong.

regards,
dan carpenter