linux-kernel - Re: [PATCH RESEND] lib: fix bitmap_parse() on 64-bit big endian archs

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Message-ID: <CAHp75VdM2yrpd2d3pK2RkmbhF3yiM4=fiTXL4i3yu3AxV3wY-A@mail.gmail.com>
Date:   Mon, 18 May 2020 14:33:43 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-s390@...r.kernel.org, Stable <stable@...r.kernel.org>,
        Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        "Tobin C . Harding" <tobin@...nel.org>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Will Deacon <will.deacon@....com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH RESEND] lib: fix bitmap_parse() on 64-bit big endian archs

On Mon, May 18, 2020 at 1:40 PM Alexander Gordeev
<agordeev@...ux.ibm.com> wrote:
>
> Commit 2d6261583be0 ("lib: rework bitmap_parse()") does
> not take into account order of halfwords on 64-bit big
> endian architectures.

Thanks for report and the patch!

Did it work before? Can we have a test case for that that we will see
the failure?

> Fixes: 2d6261583be0 ("lib: rework bitmap_parse()")
> Cc: stable@...r.kernel.org
> Cc: Yury Norov <yury.norov@...il.com>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Cc: Amritha Nambiar <amritha.nambiar@...el.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Chris Wilson <chris@...is-wilson.co.uk>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Miklos Szeredi <mszeredi@...hat.com>
> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Steffen Klassert <steffen.klassert@...unet.com>
> Cc: "Tobin C . Harding" <tobin@...nel.org>
> Cc: Vineet Gupta <vineet.gupta1@...opsys.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
> ---
>  lib/bitmap.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 89260aa..a725e46 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -717,6 +717,19 @@ static const char *bitmap_get_x32_reverse(const char *start,
>         return end;
>  }
>
> +#if defined(__BIG_ENDIAN) && defined(CONFIG_64BIT)
> +static void save_x32_chunk(unsigned long *maskp, u32 chunk, int chunk_idx)
> +{
> +       maskp += (chunk_idx / 2);
> +       ((u32 *)maskp)[(chunk_idx & 1) ^ 1] = chunk;
> +}
> +#else
> +static void save_x32_chunk(unsigned long *maskp, u32 chunk, int chunk_idx)
> +{
> +       ((u32 *)maskp)[chunk_idx] = chunk;
> +}
> +#endif
> +
>  /**
>   * bitmap_parse - convert an ASCII hex string into a bitmap.
>   * @start: pointer to buffer containing string.
> @@ -738,7 +751,8 @@ int bitmap_parse(const char *start, unsigned int buflen,
>  {
>         const char *end = strnchrnul(start, buflen, '\n') - 1;
>         int chunks = BITS_TO_U32(nmaskbits);
> -       u32 *bitmap = (u32 *)maskp;
> +       int chunk_idx = 0;
> +       u32 chunk;
>         int unset_bit;
>
>         while (1) {
> @@ -749,9 +763,11 @@ int bitmap_parse(const char *start, unsigned int buflen,
>                 if (!chunks--)
>                         return -EOVERFLOW;
>
> -               end = bitmap_get_x32_reverse(start, end, bitmap++);
> +               end = bitmap_get_x32_reverse(start, end, &chunk);
>                 if (IS_ERR(end))
>                         return PTR_ERR(end);
> +
> +               save_x32_chunk(maskp, chunk, chunk_idx++);
>         }
>
>         unset_bit = (BITS_TO_U32(nmaskbits) - chunks) * 32;
> --
> 1.8.3.1
>


-- 
With Best Regards,
Andy Shevchenko