linux-kernel - Re: [PATCH net-next v2] net: mvpp2: Don't use dynamic allocs for local variables

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Message-ID: <20180322205300.2d43d9e3@bootlin.com>
Date:   Thu, 22 Mar 2018 20:53:00 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     David Miller <davem@...emloft.net>, miquel.raynal@...tlin.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        antoine.tenart@...tlin.com, thomas.petazzoni@...tlin.com,
        gregory.clement@...tlin.com, nadavh@...vell.com,
        stefanc@...vell.com, ymarkman@...vell.com, mw@...ihalf.com
Subject: Re: [PATCH net-next v2] net: mvpp2: Don't use dynamic allocs for
 local variables

On Thu, 22 Mar 2018 15:43:08 -0400 (EDT),
David Miller <davem@...emloft.net> wrote :

> From: Maxime Chevallier <maxime.chevallier@...tlin.com>
> Date: Thu, 22 Mar 2018 20:14:53 +0100
> 
> > Hello David,
> > 
> > On Thu, 22 Mar 2018 14:47:09 -0400 (EDT),
> > David Miller <davem@...emloft.net> wrote :
> >   
> >> From: Maxime Chevallier <maxime.chevallier@...tlin.com>
> >> Date: Wed, 21 Mar 2018 16:14:00 +0100
> >> 
> >> In order to be an equivalent change you must bzero out this 'pe'
> >> object on the stack.  You are only initializing the index member
> >> before passing it into other functions.  
> > 
> > I agree that this is unclear, but the functions I pass these
> > objects to only need the index field to be set, and will fill the
> > rest of the object according to the underlying HW representation
> > (these objects mirror the HW configuration).
> > 
> > I can see that this is confusing, we might want to make the
> > mvpp2_prs_hw_read function more explicit about this.
> > 
> > Would comments explaning this be enough, or should I try another
> > way to make this cleaner ?  
> 
> Please bzero the object as I have asked you to.
> 
> Today the function doesn't care about any input members other than
> member, but in the future it might, and this is a bug waiting to
> happen.

Got it.

> It is never good to pass partially initialized variables into
> another piece of code.

Ok, I'll send another version with this.

Thanks for the review,

Maxime