linux-kernel - [PATCH 1/2] uio_hv_generic: Fix kernel NULL pointer dereference in hv_uio

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Message-Id: <20240822110912.13735-2-namjain@linux.microsoft.com>
Date: Thu, 22 Aug 2024 16:39:11 +0530
From: Naman Jain <namjain@...ux.microsoft.com>
To: "K . Y . Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>,
	Dexuan Cui <decui@...rosoft.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Stephen Hemminger <stephen@...workplumber.org>
Cc: linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Saurabh Sengar <ssengar@...ux.microsoft.com>,
	Naman Jain <namjain@...ux.microsoft.com>
Subject: [PATCH 1/2] uio_hv_generic: Fix kernel NULL pointer dereference in hv_uio_rescind

From: Saurabh Sengar <ssengar@...ux.microsoft.com>

For primary VMBus channels primary_channel pointer is always NULL. This
pointer is valid only for the secondry channels.

Fix NULL pointer dereference by retrieving the device_obj from the parent
in the absence of a valid primary_channel pointer.

Fixes: ca3cda6fcf1e ("uio_hv_generic: add rescind support")
Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
Signed-off-by: Naman Jain <namjain@...ux.microsoft.com>
---
 drivers/uio/uio_hv_generic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index b45653752301..c99890c16d29 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -109,7 +109,8 @@ static void hv_uio_channel_cb(void *context)
  */
 static void hv_uio_rescind(struct vmbus_channel *channel)
 {
-	struct hv_device *hv_dev = channel->primary_channel->device_obj;
+	struct hv_device *hv_dev = channel->primary_channel ?
+				   channel->primary_channel->device_obj : channel->device_obj;
 	struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
 
 	/*
-- 
2.34.1