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From: "Wang, Wei W" <wei.w.wang@intel.com>
To: Kunwu Chan <chentao@kylinos.cn>, "alex.williamson@redhat.com"
	<alex.williamson@redhat.com>
CC: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2] vfio: Use WARN_ON for low-probability allocation
 failure issue in vfio_pci_bus_notifier
Thread-Topic: [PATCH v2] vfio: Use WARN_ON for low-probability allocation
 failure issue in vfio_pci_bus_notifier
Thread-Index: AQHaR3z9FIdL+jn8c0+6wUQa6PWyULDa+5Eg
Date: Mon, 15 Jan 2024 15:41:02 +0000
Message-ID: <DS0PR11MB6373BAF9CFEC4D67DEAAB1F7DC6C2@DS0PR11MB6373.namprd11.prod.outlook.com>
References: <20240115063434.20278-1-chentao@kylinos.cn>
In-Reply-To: <20240115063434.20278-1-chentao@kylinos.cn>
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On Monday, January 15, 2024 2:35 PM, Kunwu Chan wrote:
> kasprintf() returns a pointer to dynamically allocated memory which can b=
e
> NULL upon failure.
>=20
> This is a blocking notifier callback, so errno isn't a proper return valu=
e. Use
> WARN_ON to small allocation failures.
>=20
> Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
> ---
> v2: Use WARN_ON instead of return errno
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 1 +
>  1 file changed, 1 insertion(+)
>=20
> 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_bl=
ock
> *nb,
>  			 pci_name(pdev));
>  		pdev->driver_override =3D 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 th=
ough
less likely? Similar examples could be found in kvm_pm_notifier_call, kasan=
_mem_notifier etc.