linux-kernel - Re: [PATCH v2] vduse: Validate vq_num in vduse_validate

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Message-ID: <20221128105312.3ajursuudvmysiie@sgarzare-redhat>
Date:   Mon, 28 Nov 2022 11:53:12 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc:     error27@...il.com, harshit.m.mogalapalli@...il.com,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xie Yongji <xieyongji@...edance.com>,
        Gautam Dawar <gautam.dawar@...inx.com>,
        Parav Pandit <parav@...dia.com>, Eli Cohen <elic@...dia.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vduse: Validate vq_num in vduse_validate_config()

On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
>Add a limit to 'config->vq_num' which is user controlled data which
>comes from an vduse_ioctl to prevent large memory allocations.
>
>This is found using static analysis with smatch.
>
>Suggested-by: Michael S. Tsirkin <mst@...hat.com>
>Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
>---
>v1->v2: Change title of the commit and description, add a limit to
>	vq_num.
>
>Note: I think here 0xffff is the max size of vring =  no: of vqueues.
>Only compile and boot tested.
>---
> drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
> 1 file changed, 3 insertions(+)
>
>diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>index 35dceee3ed56..31017ebc4d7c 100644
>--- a/drivers/vdpa/vdpa_user/vduse_dev.c
>+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>@@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
> 	if (config->config_size > PAGE_SIZE)
> 		return false;
>
>+	if (config->vq_num > 0xffff)

What about using U16_MAX here?

Thanks,
Stefano

>+		return false;
>+
> 	if (!device_is_allowed(config->device_id))
> 		return false;
>
>-- 
>2.38.1
>