Re: [PATCH 2/2] dmaengine: idxd: fix destroy of NULL or already destroyed workqueue

[Frank Li]

On Wed, Oct 28, 2026 at 12:37:07AM +0000, Jingyi Li wrote:
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>
> idxd_conf_device_release() unconditionally calls
> destroy_workqueue(idxd->wq). This is wrong in two cases:
>
>  - If idxd_probe() fails before idxd_setup_internals() has created the
>    workqueue, for example when the device reports HALTED after reset,
>    idxd->wq is still NULL and the final put_device() in the probe error
>    path oopses:
>
>    BUG: kernel NULL pointer dereference, address: 00000000000000d0
>    RIP: 0010:destroy_workqueue+0xe/0x300
>    Call Trace:
>     <TASK>
>     idxd_conf_device_release+0x15/0x90 [idxd]
>     device_release+0x3c/0x90
>     kobject_put+0x7e/0x1e0
>     idxd_pci_probe_alloc+0x300/0x15e0 [idxd]
>     local_pci_probe+0x22/0x60
>     pci_device_probe+0xd4/0x260
>
>  - idxd_cleanup_internals() and the err_evl path of
>    idxd_setup_internals() destroy the workqueue but leave idxd->wq
>    pointing to it, so the release callback destroys it a second time.
>
> Clear idxd->wq after the early destroys and skip the destroy in the
> release callback when there is no workqueue.
>
> We hit the NULL case in a kdump crash kernel, where the DSA device
> fails to reset and the oops kills the crash kernel before the dump is
> saved.
>
> Fixes: 3d33de353b1f ("dmaengine: idxd: Fix not releasing workqueue on .release()")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jingyi Li <jinli@xxxxxxxxxxxxxxx>
> ---

This one better than
https://lore.kernel.org/dmaengine/20261012-wt-idxd-fixes-v1-1-30a35a445077@xxxxxxxxx/

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/idxd/init.c  | 2 ++
>  drivers/dma/idxd/sysfs.c | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index 1577d22b299c..5962cacef060 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -389,6 +389,7 @@ static void idxd_cleanup_internals(struct idxd_device *idxd)
>         idxd_clean_engines(idxd);
>         idxd_clean_wqs(idxd);
>         destroy_workqueue(idxd->wq);
> +       idxd->wq = NULL;
>  }
>
>  static int idxd_init_evl(struct idxd_device *idxd)
> @@ -460,6 +461,7 @@ static int idxd_setup_internals(struct idxd_device *idxd)
>
>   err_evl:
>         destroy_workqueue(idxd->wq);
> +       idxd->wq = NULL;
>   err_wkq_create:
>         idxd_clean_groups(idxd);
>   err_group:
> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
> index 6d251095c350..d5ffc641c856 100644
> --- a/drivers/dma/idxd/sysfs.c
> +++ b/drivers/dma/idxd/sysfs.c
> @@ -1836,7 +1836,8 @@ static void idxd_conf_device_release(struct device *dev)
>  {
>         struct idxd_device *idxd = confdev_to_idxd(dev);
>
> -       destroy_workqueue(idxd->wq);
> +       if (idxd->wq)
> +               destroy_workqueue(idxd->wq);
>         kfree(idxd->groups);
>         bitmap_free(idxd->wq_enable_map);
>         kfree(idxd->wqs);
> --
> 2.43.0
>