Subject: Re: [PATCH v2 21/30] cxlflash: Fix to prevent workq from accessing freed memory

From: Tomas Henzl <[email-masked]>
Date: Mon, 21 Sep 2015 14:25:41 +0200

On 16.9.2015 23:31, Matthew R. Ochs wrote:
> The workq can process work in parallel with a remove event, leading
> to a condition where the workq handler can access freed memory.
>
> To remedy, the workq should be terminated prior to freeing memory. Move
> the termination call earlier in remove and use cancel_work_sync() instead
> of flush_work() as there is not a need to process any scheduled work when
> shutting down.
>
> Signed-off-by: Matthew R. Ochs <[email-masked]>
> Signed-off-by: Manoj N. Kumar <[email-masked]>
> ---
>  drivers/scsi/cxlflash/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/cxlflash/main.c b/drivers/scsi/cxlflash/main.c
> index 1856a73..1625aea 100644
> --- a/drivers/scsi/cxlflash/main.c
> +++ b/drivers/scsi/cxlflash/main.c
> @@ -736,12 +736,12 @@ static void cxlflash_remove(struct pci_dev *pdev)
>  		scsi_remove_host(cfg->host);
>  		/* Fall through */
>  	case INIT_STATE_AFU:
> +		cancel_work_sync(&cfg->work_q);
>  		term_afu(cfg);

You disable irqs after a call to cancel_work_sync.
That means a late int could trigger the workqueue again?
Please disable irqs earlier - as described in Documentation/PCI/pci.txt

>  	case INIT_STATE_PCI:
>  		pci_release_regions(cfg->dev);
>  		pci_disable_device(pdev);
>  	case INIT_STATE_NONE:
> -		flush_work(&cfg->work_q);
>  		free_mem(cfg);
>  		scsi_host_put(cfg->host);
>  		break;