linux-kernel - [PATCH] ipmi: code cleanup and prevent potential issue.

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Date:   Tue,  9 Jun 2020 01:04:10 -0500
From:   wu000273@....edu
To:     kjlu@....edu
Cc:     wu000273@....edu, Corey Minyard <minyard@....org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: [PATCH] ipmi: code cleanup and prevent potential issue.

From: Qiushi Wu <wu000273@....edu>

All the previous get/put operations against intf->refcount are
inside the mutex. Thus, put the last kref_put() also inside mutex
to make sure get/put functions execute in order and prevent the
potential race condition.

Signed-off-by: Qiushi Wu <wu000273@....edu>
---
 drivers/char/ipmi/ipmi_msghandler.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index e1b22fe0916c..d34343e34272 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -2583,10 +2583,11 @@ static int __bmc_get_device_id(struct ipmi_smi *intf, struct bmc_device *bmc,
 			*guid =  bmc->guid;
 	}
 
+	kref_put(&intf->refcount, intf_free);
+
 	mutex_unlock(&bmc->dyn_mutex);
 	mutex_unlock(&intf->bmc_reg_mutex);
 
-	kref_put(&intf->refcount, intf_free);
 	return rv;
 }
 
-- 
2.17.1