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Message-ID: <d2b2baca-589d-83ef-04b0-0f64b18f9d95@wanadoo.fr>
Date:   Tue, 18 Apr 2023 20:05:54 +0200
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Subject: Re: [PATCH RESEND] sh: sq: Use the bitmap API when applicable
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To:     Geert Uytterhoeven <geert@linux-m68k.org>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc:     Yoshinori Sato <ysato@users.sourceforge.jp>,
        Rich Felker <dalias@libc.org>, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org, linux-sh@vger.kernel.org
References: <071e9f32c19a007f4922903282c9121898641400.1681671848.git.christophe.jaillet@wanadoo.fr>
 <b5fea49d68e1e2a702b0050f73582526e205cfa2.camel@physik.fu-berlin.de>
 <CAMuHMdWz7YJ4ifkxU2GGdoj46fTsjS5WE66R0YzvOYr1ZKY=4w@mail.gmail.com>
From:   Christophe JAILLET <christophe.jaillet@wanadoo.fr>
In-Reply-To: <CAMuHMdWz7YJ4ifkxU2GGdoj46fTsjS5WE66R0YzvOYr1ZKY=4w@mail.gmail.com>
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Le 18/04/2023 à 09:14, Geert Uytterhoeven a écrit :
> 
> Nice catch!
> 
> Looking more deeply at the code, the intention is to allocate a bitmap
> with nr_pages bits, so the code fater Christophe's patch is correct.
> However, the old code is indeed wrong:
> 
>      (nr_pages + (BITS_PER_LONG - 1)) / BITS_PER_LONG
> 
> The aim is to calculate the size in bytes, rounded up to an integral
> number of longs, but it lacks a final multiplication by BITS_PER_BYTE,
> so it's off by a factor of 4.
> 
> Fixes: d7c30c682a278abe ("sh: Store Queue API rework.")
> 
> As we didn't have bitmap_zalloc() until commit c42b65e363ce97a8
> ("bitmap: Add bitmap_alloc(), bitmap_zalloc() and bitmap_free()")
> in v4.19, it would be good to fix the bug first in a separate patch,
> not using
> 
> BTW, interesting how this got missed when fixing the other out-of-range
> bug in commit 9f650cf2b811cfb6 ("sh: Fix store queue bitmap end.",
> s/marc.theaimsgroup.com/marc.info/ when following the link).

So, this means that this got unnoticed for 16 years?
Waouh!

I would never have thought that a "trivial" clean-up that I took time to 
repost could trigger such a thing!

Again.
Waouh!


Maybe, 0x04000000 is way to big?
Anyone knows where this value comes from?

Could there have been some memory corruption in real world application?

CJ

> 
> Gr{oetje,eeting}s,
> 
>                          Geert
>