linux-kernel - Re: [PATCH 1/4] sparc32: mm: Fix argument checking in __srmmu_get

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Message-ID: <CAKwvOdm9q0wPun0zLcFB0Z5NPec08OpHWp3tJV3-ddFiuU2jQA@mail.gmail.com>
Date:   Tue, 24 Mar 2020 11:04:23 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...roid.com>,
        "David S. Miller" <davem@...emloft.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        sparclinux@...r.kernel.org
Subject: Re: [PATCH 1/4] sparc32: mm: Fix argument checking in __srmmu_get_nocache()

On Tue, Mar 24, 2020 at 10:51 AM Will Deacon <will@...nel.org> wrote:
>
> On Tue, Mar 24, 2020 at 10:41:52AM -0700, Nick Desaulniers wrote:
> > On Tue, Mar 24, 2020 at 3:52 AM Will Deacon <will@...nel.org> wrote:
> > >
> > > The 'size' argument to __srmmu_get_nocache() is a number of bytes not
> > > a shift value, so fix up the sanity checking to treat it properly.
> > >
> > > Cc: "David S. Miller" <davem@...emloft.net>
> > > Cc: Peter Zijlstra <peterz@...radead.org>
> > > Signed-off-by: Will Deacon <will@...nel.org>
> > > ---
> > >  arch/sparc/mm/srmmu.c | 12 ++++++------
> > >  1 file changed, 6 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
> > > index f56c3c9a9793..a19863cac0c4 100644
> > > --- a/arch/sparc/mm/srmmu.c
> > > +++ b/arch/sparc/mm/srmmu.c
> > > @@ -175,18 +175,18 @@ pte_t *pte_offset_kernel(pmd_t *dir, unsigned long address)
> > >   */
> > >  static void *__srmmu_get_nocache(int size, int align)
> > >  {
> > > -       int offset;
> > > +       int offset, minsz = 1 << SRMMU_NOCACHE_BITMAP_SHIFT;
> > >         unsigned long addr;
> > >
> > > -       if (size < SRMMU_NOCACHE_BITMAP_SHIFT) {
> > > +       if (size < minsz) {
> > >                 printk(KERN_ERR "Size 0x%x too small for nocache request\n",
> > >                        size);
> > > -               size = SRMMU_NOCACHE_BITMAP_SHIFT;
> > > +               size = minsz;
> > >         }
> > > -       if (size & (SRMMU_NOCACHE_BITMAP_SHIFT - 1)) {
> > > -               printk(KERN_ERR "Size 0x%x unaligned int nocache request\n",
> > > +       if (size & (minsz - 1)) {
> > > +               printk(KERN_ERR "Size 0x%x unaligned in nocache request\n",
> >
> > Was modifying the printk intentional? int vs in ?
>
> Yes, I think "int" is a typo so I just fixed it up while I was here. Do you
> prefer the old way? I couldn't parse it at first, but now you mention it
> I suppose the type of 'size' is int, so *maybe* it makes sense after all!

No preference; the code is validating/updating the `size` which as you
noted is an `int`.

-- 
Thanks,
~Nick Desaulniers