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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>
CC:     "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hardening@vger.kernel.org" <linux-hardening@vger.kernel.org>
Subject: RE: [PATCH][next] Drivers: hv: vmbus: Use struct_size() helper in
 kmalloc()
Thread-Topic: [PATCH][next] Drivers: hv: vmbus: Use struct_size() helper in
 kmalloc()
Thread-Index: AQHYEikr/2Ofcu6A+U68I3R7gLJE+Kx3CXyA
Date:   Thu, 27 Jan 2022 16:01:28 +0000
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From: Gustavo A. R. Silva <gustavoars@kernel.org> Sent: Tuesday, January 25=
, 2022 10:02 AM
>=20
> Make use of the struct_size() helper instead of an open-coded version,
> in order to avoid any potential type mistakes or integer overflows that,
> in the worst scenario, could lead to heap overflows.
>=20
> Also, address the following sparse warnings:
> drivers/hv/vmbus_drv.c:1132:31: warning: using sizeof on a flexible struc=
ture
>=20
> Link: https://github.com/KSPP/linux/issues/174
> ---
>  drivers/hv/vmbus_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 17bf55fe3169..cd193456cd84 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1129,7 +1129,7 @@ void vmbus_on_msg_dpc(unsigned long data)
>  	}
>=20
>  	if (entry->handler_type	=3D=3D VMHT_BLOCKING) {
> -		ctx =3D kmalloc(sizeof(*ctx) + payload_size, GFP_ATOMIC);
> +		ctx =3D kmalloc(struct_size(ctx, msg.payload, payload_size), GFP_ATOMI=
C);
>  		if (ctx =3D=3D NULL)
>  			return;
>=20
> --
> 2.27.0

Reviewed-by: Michael Kelley <mikelley@microsoft.com>