linux-kernel - [PATCH v3] vduse: Validate vq_num in vduse_validate

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Message-Id: <20221128155717.2579992-1-harshit.m.mogalapalli@oracle.com>
Date:   Mon, 28 Nov 2022 07:57:15 -0800
From:   Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To:     sgarzare@...hat.com
Cc:     harshit.m.mogalapalli@...cle.com, 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>,
        Maxime Coquelin <maxime.coquelin@...hat.com>,
        Parav Pandit <parav@...dia.com>, Eli Cohen <elic@...dia.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3] vduse: Validate vq_num in vduse_validate_config()

Add a limit to 'config->vq_num' which is user controlled data which
comes from an vduse_ioctl to prevent large memory allocations.

Micheal says  - This limit is somewhat arbitrary.
However, currently virtio pci and ccw are limited to a 16 bit vq number.
While MMIO isn't it is also isn't used with lots of VQs due to
current lack of support for per-vq interrupts.
Thus, the 0xffff limit on number of VQs corresponding
to a 16-bit VQ number seems sufficient for now.

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.

v2->v3: Improve commit message to include reason for setting limit to
	0xffff

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