[PATCH] w1_therm: Free the correct variable

[PATCH] w1_therm: Free the correct variable

[Dan Carpenter]

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@oracle.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

Re: [PATCH] w1_therm: Free the correct variable

[Akira shimahara]

Hi,

Le mercredi 20 mai 2020 à 15:00 +0300, Dan Carpenter a écrit :
> 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@oracle.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;
>  }

I tested it on several devices to be safe, no issue at runtime.
Sorry for the mistake and thanks for the fix.

Akira Shimahara