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From:   Marco Elver <elver@google.com>
Date:   Thu, 13 Jun 2019 14:35:17 +0200
Message-ID: <CANpmjNNz8-dfnSXGouHQJqg+zBHJWVPmCM9Ggxj_LAb4VeOocg@mail.gmail.com>
Subject: Re: [PATCH v3 1/3] lib/test_kasan: Add bitops tests
To:     Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Mark Rutland <mark.rutland@arm.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>
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Thanks, I've sent v4.

On Thu, 13 Jun 2019 at 12:49, Andrey Ryabinin <aryabinin@virtuozzo.com> wrote:
>
>
>
> On 5/31/19 6:08 PM, Marco Elver wrote:
> > This adds bitops tests to the test_kasan module. In a follow-up patch,
> > support for bitops instrumentation will be added.
> >
> > Signed-off-by: Marco Elver <elver@google.com>
> > ---
> > Changes in v3:
> > * Use kzalloc instead of kmalloc.
> > * Use sizeof(*bits).
> >
> > Changes in v2:
> > * Use BITS_PER_LONG.
> > * Use heap allocated memory for test, as newer compilers (correctly)
> >   warn on OOB stack access.
> > ---
> >  lib/test_kasan.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 72 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> > index 7de2702621dc..1ef9702327d2 100644
> > --- a/lib/test_kasan.c
> > +++ b/lib/test_kasan.c
> > @@ -11,16 +11,17 @@
> >
> >  #define pr_fmt(fmt) "kasan test: %s " fmt, __func__
> >
> > +#include <linux/bitops.h>
> >  #include <linux/delay.h>
> > +#include <linux/kasan.h>
> >  #include <linux/kernel.h>
> > -#include <linux/mman.h>
> >  #include <linux/mm.h>
> > +#include <linux/mman.h>
> > +#include <linux/module.h>
> >  #include <linux/printk.h>
> >  #include <linux/slab.h>
> >  #include <linux/string.h>
> >  #include <linux/uaccess.h>
> > -#include <linux/module.h>
> > -#include <linux/kasan.h>
> >
> >  /*
> >   * Note: test functions are marked noinline so that their names appear in
> > @@ -623,6 +624,73 @@ static noinline void __init kasan_strings(void)
> >       strnlen(ptr, 1);
> >  }
> >
> > +static noinline void __init kasan_bitops(void)
> > +{
> > +     long *bits = kzalloc(sizeof(*bits), GFP_KERNEL);
>
> It would be safer to do kzalloc(sizeof(*bits) + 1, GFP_KERNEL) and change tests accordingly to: set_bit(BITS_PER_LONG + 1, bits) ...
> kmalloc will internally round up allocation to 16-bytes, so we won't be actually corrupting someone elses memory.
>
>
> > +     if (!bits)
> > +             return;
> > +
> > +     pr_info("within-bounds in set_bit");
> > +     set_bit(0, bits);
> > +
> > +     pr_info("within-bounds in set_bit");
> > +     set_bit(BITS_PER_LONG - 1, bits);
>
>
> I'd remove these two. There are plenty of within bounds set_bit() in the kernel so they are well tested already.
>
> --
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