Re: [PATCH v2] dmaengine: idxd: Fix use-after-free of idxd_wq

[Guixin Liu <kanie@linux.alibaba.com>]

Hi Vinod, could you please apply this patch? 
This patch was from a long time ago.

Best Regards,
Guixin Liu

在 2026/4/15 17:50, Guixin Liu 写道:
> We found an idxd_wq use-after-free issue with kasan
> when remove the idxd PCI device:
>
> BUG: KASAN: slab-use-after-free in idxd_device_drv_remove+0x1f8/0x240 [idxd]
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0x32/0x50
>   print_address_description.constprop.0+0x2c/0x390
>   ? idxd_device_drv_remove+0x1f8/0x240 [idxd]
>   print_report+0xba/0x280
>   ? kasan_addr_to_slab+0x9/0xa0
>   ? idxd_device_drv_remove+0x1f8/0x240 [idxd]
>   kasan_report+0xab/0xe0
>   ? idxd_device_drv_remove+0x1f8/0x240 [idxd]
>   idxd_device_drv_remove+0x1f8/0x240 [idxd]
>   device_release_driver_internal+0x391/0x560
>   bus_remove_device+0x1f5/0x3f0
>   device_del+0x392/0x990
>   ? __pfx_device_del+0x10/0x10
>   ? kobject_cleanup+0x117/0x360
>   ? idxd_unregister_devices+0x229/0x320 [idxd]
>   device_unregister+0x13/0xa0
>   idxd_remove+0x4f/0x1b0 [idxd]
>   pci_device_remove+0xa7/0x1d0
>   device_release_driver_internal+0x391/0x560
>   ? pci_pme_active+0x1e/0x450
>   pci_stop_bus_device+0x10a/0x150
>   pci_stop_and_remove_bus_device_locked+0x16/0x30
>   remove_store+0xcf/0xe0
>
> Freed by task 15535:
>   kasan_save_stack+0x1c/0x40
>   kasan_set_track+0x21/0x30
>   kasan_save_free_info+0x27/0x40
>   ____kasan_slab_free+0x171/0x240
>   slab_free_freelist_hook+0xde/0x190
>   __kmem_cache_free+0x19e/0x310
>   device_release+0x98/0x210
>   kobject_cleanup+0x102/0x360
>   idxd_unregister_devices+0xb3/0x320 [idxd]
>   dxd_remove+0x3f/0x1b0 [idxd]
>   pci_device_remove+0xa7/0x1d0
>   device_release_driver_internal+0x391/0x560
>   pci_stop_bus_device+0x10a/0x150
>   pci_stop_and_remove_bus_device_locked+0x16/0x30
>   remove_store+0xcf/0xe0
>
> In the idxd_remove() flow, when execution reaches
> idxd_unregister_devices(), all idxd_wq instances have already been
> freed. Subsequently, when device_unregister(idxd_confdev(idxd)) is
> executed, it calls into idxd_device_drv_remove() which accesses the
> already-freed idxd_wq. This fix resolves the issue by calling
> device_release_driver() before idxd_unregister_devices().
>
> Fixes: 98da0106aac0d ("dmanegine: idxd: fix resource free ordering on driver removal")
> Co-developed-by: Shuai Xue <xueshuai@linux.alibaba.com>
> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
> ---
> v1 -> v2:
>   1. Call device_release_driver() in advance instead of swapping the order of
>      device_unregister() and idxd_unregister_devices().
>   2. Add Co-developed-by: Shuai Xue <xueshuai@linux.alibaba.com>.
>  drivers/dma/idxd/init.c | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> index f1cfc7790d95..3b0a0363ca65 100644
> --- a/drivers/dma/idxd/init.c
> +++ b/drivers/dma/idxd/init.c
> @@ -1293,13 +1293,30 @@ static void idxd_remove(struct pci_dev *pdev)
>  {
>  	struct idxd_device *idxd = pci_get_drvdata(pdev);
>  
> +	/*
> +	 * The idxd sub-driver's remove callback (idxd_device_drv_remove())
> +	 * iterates idxd->wqs[] and accesses wq objects. We must unbind the
> +	 * sub-driver before idxd_unregister_devices() frees these objects,
> +	 * otherwise a use-after-free occurs.
> +	 *
> +	 * We cannot simply reorder device_unregister(idxd_confdev) before
> +	 * idxd_unregister_devices() because device_del() -> kobject_del()
> +	 * recursively removes the parent's sysfs directory, which destroys
> +	 * children's sysfs entries. Subsequent device_unregister() on the
> +	 * children then fails with "sysfs group 'power' not found".
> +	 *
> +	 * Use device_release_driver() to only unbind the driver (triggering
> +	 * idxd_device_drv_remove()) without touching sysfs. Then safely
> +	 * unregister children before the parent.
> +	 */
> +	device_release_driver(idxd_confdev(idxd));
>  	idxd_unregister_devices(idxd);
> +
>  	/*
> -	 * When ->release() is called for the idxd->conf_dev, it frees all the memory related
> -	 * to the idxd context. The driver still needs those bits in order to do the rest of
> -	 * the cleanup. However, we do need to unbound the idxd sub-driver. So take a ref
> -	 * on the device here to hold off the freeing while allowing the idxd sub-driver
> -	 * to unbind.
> +	 * When ->release() is called for the idxd->conf_dev, it frees all the
> +	 * memory related to the idxd context. The driver still needs those bits
> +	 * in order to do the rest of the cleanup. So take a ref on the device
> +	 * here to hold off the freeing.
>  	 */
>  	get_device(idxd_confdev(idxd));
>  	device_unregister(idxd_confdev(idxd));