linux-kernel - Re: [PATCH 1/1] tty: vt: Remove redundant null check before kfree.

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Message-ID: <CAK9yfHw=AjCQ+1VsXLZa=wtNopoZxSsd3xSa+_UDNYOOohY2dg@mail.gmail.com>
Date:	Wed, 21 Nov 2012 20:59:08 +0530
From:	Sachin Kamat <sachin.kamat@...aro.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, patches@...aro.org
Subject: Re: [PATCH 1/1] tty: vt: Remove redundant null check before kfree.

On 21 November 2012 20:46, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Wed, Nov 21, 2012 at 08:21:40PM +0530, Sachin Kamat wrote:
>> On 21 November 2012 20:16, Greg KH <gregkh@...uxfoundation.org> wrote:
>> > On Wed, Nov 21, 2012 at 10:49:07AM +0530, Sachin Kamat wrote:
>> >> kfree on a NULL pointer is a no-op.
>> >>
>> >> Signed-off-by: Sachin Kamat <sachin.kamat@...aro.org>
>> >> ---
>> >>  drivers/tty/vt/consolemap.c |    6 ++----
>> >>  1 files changed, 2 insertions(+), 4 deletions(-)
>> >>
>> >> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
>> >> index 2aaa0c2..248381b 100644
>> >> --- a/drivers/tty/vt/consolemap.c
>> >> +++ b/drivers/tty/vt/consolemap.c
>> >> @@ -410,10 +410,8 @@ static void con_release_unimap(struct uni_pagedir *p)
>> >>               kfree(p->inverse_translations[i]);
>> >>               p->inverse_translations[i] = NULL;
>> >>       }
>> >> -     if (p->inverse_trans_unicode) {
>> >> -             kfree(p->inverse_trans_unicode);
>> >> -             p->inverse_trans_unicode = NULL;
>> >> -     }
>> >> +     kfree(p->inverse_trans_unicode);
>> >> +     p->inverse_trans_unicode = NULL;
>> >
>> > kfree with NULL is a no-op, but the line after that just caused a kernel
>> > crash if it was NULL, so I can't accept this type of thing.
>> >
>> > Please be more careful.
>>
>> My mistake. Apologies for the same.
>>
>> Do we need to assign the pointer to NULL after freeing?
>
> It depends if it is checked later on, is it?

I will re-send this patch after deleting the assignment?

>
>> > What's with the patches@...aro.org email address?  What is that for?
>> That is a logging mechanism (done by patchwork) for all patches sent
>> by Linaro engineers.
>
> So you can track it internally?  Why?

Yes. For tracking the status.
>
> greg k-h



-- 
With warm regards,
Sachin
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