linux-kernel - RE: [PATCH 1/3] x86/MCE/AMD: Redo function to get SMCA bank type

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Date:   Wed, 14 Feb 2018 16:38:34 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bp@...e.de" <bp@...e.de>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH 1/3] x86/MCE/AMD: Redo function to get SMCA bank type

> -----Original Message-----
> From: Borislav Petkov [mailto:bp@...en8.de]
> Sent: Thursday, February 8, 2018 10:05 AM
> To: Ghannam, Yazen <Yazen.Ghannam@....com>
> Cc: linux-edac@...r.kernel.org; linux-kernel@...r.kernel.org; bp@...e.de;
> tony.luck@...el.com; x86@...nel.org
> Subject: Re: [PATCH 1/3] x86/MCE/AMD: Redo function to get SMCA bank type
> 
> On Thu, Feb 01, 2018 at 12:48:11PM -0600, Yazen Ghannam wrote:
> >  arch/x86/kernel/cpu/mcheck/mce_amd.c | 15 +++++++--------
> >  1 file changed, 7 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> > index 0f32ad242324..4e16afc0794d 100644
> > --- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
> > +++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
> > @@ -110,14 +110,14 @@ const char *smca_get_long_name(enum
> smca_bank_types t)
> >  }
> >  EXPORT_SYMBOL_GPL(smca_get_long_name);
> >
> > -static enum smca_bank_types smca_get_bank_type(struct mce *m)
> > +static enum smca_bank_types smca_get_bank_type(unsigned int bank)
> >  {
> >  	struct smca_bank *b;
> >
> > -	if (m->bank >= N_SMCA_BANK_TYPES)
> > +	if (bank >= ARRAY_SIZE(smca_banks))
> 
> MAX_NR_BANKS
> 

I know that we're declaring smca_banks[] to have MAX_NR_BANKS items. But
shouldn't we directly check that an index is within the bounds of the array?
We'll have a bug if we check against MAX_NR_BANKS and the definition of
smca_banks[] changes.

Thanks,
Yazen