RE: [PATCH v2] vfio: Use WARN_ON for low-probability allocation failure issue in vfio_pci_bus_notifier

[Wang, Wei W]

On Monday, January 15, 2024 2:35 PM, Kunwu Chan wrote:
> kasprintf() returns a pointer to dynamically allocated memory which can be
> NULL upon failure.
> 
> This is a blocking notifier callback, so errno isn't a proper return value. Use
> WARN_ON to small allocation failures.
> 
> Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
> ---
> v2: Use WARN_ON instead of return errno
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 1cbc990d42e0..61aa19666050 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -2047,6 +2047,7 @@ static int vfio_pci_bus_notifier(struct notifier_block
> *nb,
>  			 pci_name(pdev));
>  		pdev->driver_override = kasprintf(GFP_KERNEL, "%s",
>  						  vdev->vdev.ops->name);
> +		WARN_ON(!pdev->driver_override);

Saw Alex's comments on v1. Curious why not return "NOTIFY_BAD" on errors though
less likely? Similar examples could be found in kvm_pm_notifier_call, kasan_mem_notifier etc.