linux-kernel - [PATCH] virt: vbox: Sanity-check parameter types for hgcm-calls coming from userspace

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Date:   Thu,  4 Apr 2019 14:39:09 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Hans de Goede <hdegoede@...hat.com>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: [PATCH] virt: vbox: Sanity-check parameter types for hgcm-calls coming from userspace

Userspace can make host function calls, called hgcm-calls through the
/dev/vboxguest device.

In this case we should not accept all hgcm-function-parameter-types, some
are only valid for in kernel calls.

This commit adds proper hgcm-function-parameter-type validation to the
ioctl for doing a hgcm-call from userspace.

Cc: stable@...r.kernel.org
Signed-off-by: Hans de Goede <hdegoede@...hat.com>
---
 drivers/virt/vboxguest/vboxguest_core.c | 31 +++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/virt/vboxguest/vboxguest_core.c b/drivers/virt/vboxguest/vboxguest_core.c
index 8ca333f21292..2307b0329aec 100644
--- a/drivers/virt/vboxguest/vboxguest_core.c
+++ b/drivers/virt/vboxguest/vboxguest_core.c
@@ -1298,6 +1298,20 @@ static int vbg_ioctl_hgcm_disconnect(struct vbg_dev *gdev,
 	return ret;
 }
 
+static bool vbg_param_valid(enum vmmdev_hgcm_function_parameter_type type)
+{
+	switch (type) {
+	case VMMDEV_HGCM_PARM_TYPE_32BIT:
+	case VMMDEV_HGCM_PARM_TYPE_64BIT:
+	case VMMDEV_HGCM_PARM_TYPE_LINADDR:
+	case VMMDEV_HGCM_PARM_TYPE_LINADDR_IN:
+	case VMMDEV_HGCM_PARM_TYPE_LINADDR_OUT:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static int vbg_ioctl_hgcm_call(struct vbg_dev *gdev,
 			       struct vbg_session *session, bool f32bit,
 			       struct vbg_ioctl_hgcm_call *call)
@@ -1333,6 +1347,23 @@ static int vbg_ioctl_hgcm_call(struct vbg_dev *gdev,
 	}
 	call->hdr.size_out = actual_size;
 
+	/* Validate parameter types */
+	if (f32bit) {
+		struct vmmdev_hgcm_function_parameter32 *parm =
+			VBG_IOCTL_HGCM_CALL_PARMS32(call);
+
+		for (i = 0; i < call->parm_count; i++)
+			if (!vbg_param_valid(parm[i].type))
+				return -EINVAL;
+	} else {
+		struct vmmdev_hgcm_function_parameter *parm =
+			VBG_IOCTL_HGCM_CALL_PARMS(call);
+
+		for (i = 0; i < call->parm_count; i++)
+			if (!vbg_param_valid(parm[i].type))
+				return -EINVAL;
+	}
+
 	/*
 	 * Validate the client id.
 	 */
-- 
2.21.0