linux-kernel - [PATCH] w1_therm: Free the correct variable

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Message-ID: <20200520120019.GA172354@mwanda>
Date:   Wed, 20 May 2020 15:00:19 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Evgeniy Polyakov <zbr@...emap.net>,
        Akira Shimahara <akira215corp@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Richard Fontana <rfontana@...hat.com>,
        Allison Randal <allison@...utok.net>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] w1_therm: Free the correct variable

The problem is that we change "p_args" to point to the middle of the
string so when we free it at the end of the function it's not freeing
the same pointer that we originally allocated.

Fixes: e2c94d6f5720 ("w1_therm: adding alarm sysfs entry")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
>From static analysis.  I guess it must not cause too much of a problem
at run time?

 drivers/w1/slaves/w1_therm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index cc4b88056b33..a6c85e486671 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -1526,8 +1526,9 @@ static ssize_t alarms_store(struct device *device,
 	int temp, ret = -EINVAL;
 	char *token = NULL;
 	s8 tl, th, tt;	/* 1 byte per value + temp ring order */
-	char *p_args = kmalloc(size, GFP_KERNEL);
+	char *p_args, *orig;
 
+	p_args = orig = kmalloc(size, GFP_KERNEL);
 	/* Safe string copys as buf is const */
 	if (!p_args) {
 		dev_warn(device,
@@ -1611,7 +1612,7 @@ static ssize_t alarms_store(struct device *device,
 
 free_m:
 	/* free allocated memory */
-	kfree(p_args);
+	kfree(orig);
 
 	return size;
 }
-- 
2.26.2