Hi (Assigning NULL to variable after freeing it).

Hi (Assigning NULL to variable after freeing it).

[Jose Bale]

Hi All,

I have just started to contribute to linux kernel. I was thinking of
giving a patch where a variable is made null after free if not already
done.

Some thing like this:
Original code:
  kfree(x);
  ...........some other code...........

I will change this code to:
New code:
  kfree(x);
++ x = NULL;
  ...........some other code...........

Will this kind of code change be accepted by linux kernel?

Also, isn't doing this a better practice - that is, assigning NULL to
variable after freeing it? What is the best practice? What do people
think about it?

Any feedback / replies will be greatly appreciated.

Regards,
JB

Fwd: Hi (Assigning NULL to variable after freeing it).

[Jose Bale]

Hi All,

I have just started to contribute to linux kernel. I was thinking of
giving a patch where a variable is made null after free if not already
done.

Some thing like this:
Original code:
  kfree(x);
  ...........some other code...........

I will change this code to:
New code:
  kfree(x);
++ x = NULL;
  ...........some other code...........

Will this kind of code change be accepted by linux kernel?

Also, isn't doing this a better practice - that is, assigning NULL to
variable after freeing it? What is the best practice? What do people
think about it?

Any feedback / replies will be greatly appreciated.

Regards,
JB

Re: Hi (Assigning NULL to variable after freeing it).

[Randy Dunlap]

On 01/17/18 02:44, Jose Bale wrote:
> Hi All,
> 
> I have just started to contribute to linux kernel. I was thinking of
> giving a patch where a variable is made null after free if not already
> done.
> 
> Some thing like this:
> Original code:
>   kfree(x);
>   ...........some other code...........
> 
> I will change this code to:
> New code:
>   kfree(x);
> ++ x = NULL;
>   ...........some other code...........
> 
> Will this kind of code change be accepted by linux kernel?
> 
> Also, isn't doing this a better practice - that is, assigning NULL to
> variable after freeing it? What is the best practice? What do people
> think about it?
> 
> Any feedback / replies will be greatly appreciated.

General answer is no... unless that particular code expects a freed pointer
to be null.  In many cases the code is written so that this isn't needed,
so you would have to check each usage on a case-by-case basis.

Probably best to find something else to patch.

-- 
~Randy