Re: [PATCH] m68k: fix find_next bitops

Re: [PATCH] m68k: fix find_next bitops

[Geert Uytterhoeven]

On Fri, Mar 25, 2011 at 12:00, Akinobu Mita <akinobu.mita@gmail.com> wrote:
> find_next bitops on m68k (find_next_zero_bit, find_next_bit, and
> find_next_bit_le) may cause out of bounds memory access
> when the bitmap size in bits % 32 != 0 and offset (the bitnumber
> to start searching at) is very close to the bitmap size.
>
> For example,
>
>       unsigned long bitmap[2] = { 0, 0 };
>       find_next_bit(bitmap, 63, 62);
>
> 1. find_next_bit() tries to find any set bits in bitmap[1],
>   but no bits set.
>
> 2. Then find_first_bit(bimap + 2, -1)
>
> 3. Unfortunately find_fist_bit() takes unsigned int as the size argument.
>
> 4. find_first_bit will access bitmap[2~] until it find any set bits.
>
> This switches find_next bitops to use generic implementation of
> find bitops to fix the problem.

Andreas, do you think it's worth keeping (and fixing) the m68k "optimized"
versions?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH] m68k: fix find_next bitops

[Andreas Schwab]

Geert Uytterhoeven <geert@linux-m68k.org> writes:

> Andreas, do you think it's worth keeping (and fixing) the m68k "optimized"
> versions?

Should be easy to add the required offset >= size checks.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH] m68k: fix find_next bitops

[Akinobu Mita]

2011/3/31 Andreas Schwab <schwab@linux-m68k.org>:
> Geert Uytterhoeven <geert@linux-m68k.org> writes:
>
>> Andreas, do you think it's worth keeping (and fixing) the m68k "optimized"
>> versions?
>
> Should be easy to add the required offset >= size checks.

OK, I'll try to fix the optimized version.
Or, could someone who can test on the real hardware fix this problem?

Re: [PATCH] m68k: fix find_next bitops

[Geert Uytterhoeven]

On Thu, Mar 31, 2011 at 08:02, Akinobu Mita <akinobu.mita@gmail.com> wrote:
> 2011/3/31 Andreas Schwab <schwab@linux-m68k.org>:
>> Geert Uytterhoeven <geert@linux-m68k.org> writes:
>>
>>> Andreas, do you think it's worth keeping (and fixing) the m68k "optimized"
>>> versions?
>>
>> Should be easy to add the required offset >= size checks.
>
> OK, I'll try to fix the optimized version.
> Or, could someone who can test on the real hardware fix this problem?

I'll have a look...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds