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

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Message-ID: <20200324175113.GA16742@willie-the-truck>
Date:   Tue, 24 Mar 2020 17:51:14 +0000
From:   Will Deacon <will@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
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 10:41:52AM -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!

Will