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From:   Yang Yingliang <yangyingliang@huawei.com>
To:     <linux-kernel@vger.kernel.org>
CC:     <lee@kernel.org>, <krzysztof.kozlowski@canonical.com>
Subject: [PATCH] mfd: core: fix UAF while using device of node
Date:   Wed, 16 Nov 2022 15:41:16 +0800
Message-ID: <20221116074116.1022139-1-yangyingliang@huawei.com>
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I got the following UAF report:

  refcount_t: underflow; use-after-free.
  WARNING: CPU: 1 PID: 270 at lib/refcount.c:29 refcount_warn_saturate+0x121/0x180
  ...
  OF: ERROR: memory leak, expected refcount 1 instead of -1073741824,
  of_node_get()/of_node_put() unbalanced - destroy cset entry:
  attach overlay node /i2c/pmic@62/powerkey

The of_node of device assigned in mfd_match_of_node_to_dev() need be
get, and it will be put in platform_device_release().

Fixes: 002be8114007 ("mfd: core: Add missing of_node_put for loop iteration")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/mfd/mfd-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
index 16d1861e9682..8e57f67719cf 100644
--- a/drivers/mfd/mfd-core.c
+++ b/drivers/mfd/mfd-core.c
@@ -161,7 +161,7 @@ static int mfd_match_of_node_to_dev(struct platform_device *pdev,
 	of_entry->np = np;
 	list_add_tail(&of_entry->list, &mfd_of_node_list);
 
-	pdev->dev.of_node = np;
+	pdev->dev.of_node = of_node_get(np);
 	pdev->dev.fwnode = &np->fwnode;
 #endif
 	return 0;
-- 
2.25.1