linux-kernel - Re: [PATCH v2] EFI loader: remove redundant code

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Date:   Wed, 2 Nov 2016 16:56:03 +0300
From:   Eugene Korenevsky <ekorenevsky@...il.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Linn Crosetto <linn@....com>, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v2] EFI loader: remove redundant code

> > *e820ext is always NULL in 'alloc_e820ext()' (see the code of 'exit_boot()').
> > Without loss of generality we can replace freeing with returning
> > EFI_INVALID_PARAMETER. So if the caller would ever incorrectly pass non-NULL
> > *e820ext, he will obtain a returned error code.
> >
> 
> What exactly are you trying to fix here? Adding new artificial failure
> modes is hardly worth it when all you are doing is cleaning up code
> that by itself is correct to begin with, but is simply never called.

This code (free_pool, assignments) is dead whether it is correct or
not. So it is to be removed.
The check gives some assurance that memory is not leaked if the calling
code is changed.


> > @@ -956,11 +956,8 @@ static efi_status_t alloc_e820ext(u32 nr_desc, struct setup_data **e820ext,
> >         size = sizeof(struct setup_data) +
> >                 sizeof(struct e820entry) * nr_desc;
> >
> > -       if (*e820ext) {
> > -               efi_call_early(free_pool, *e820ext);
> > -               *e820ext = NULL;
> > -               *e820ext_size = 0;
> > -       }
> > +       if (*e820ext)
> > +               return EFI_INVALID_PARAMETER;
> >
> >         status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
> >                                 size, (void **)e820ext);
> > --


-- 
Eugene