linux-kernel - Re: [PATCH] pstore/ram: Validate ECC parameters against Reed-Solomon constraint

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Message-ID: <CAHYWnBHLhOU+CJC9ViYCntSkercz4hHVnzaeEBeqchKLz7XFNA@mail.gmail.com>
Date: Mon, 23 Jun 2025 13:37:26 +0900
From: Naoya Tezuka <naoyatezuka@...gle.com>
To: Tzung-Bi Shih <tzungbi@...nel.org>
Cc: Naoya Tezuka <naoyatezuka@...omium.org>, Kees Cook <kees@...nel.org>, 
	Tony Luck <tony.luck@...el.com>, "Guilherme G . Piccoli" <gpiccoli@...lia.com>, 
	linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pstore/ram: Validate ECC parameters against Reed-Solomon constraint

Hi Tzung-Bi and others,

I truly appreciate your time and feedback on my patch.

On Mon, Jun 23, 2025 at 12:03 PM Tzung-Bi Shih <tzungbi@...nel.org> wrote:
>
> On Fri, Jun 20, 2025 at 02:47:57PM +0900, Naoya Tezuka wrote:
> > The Reed-Solomon library enforces the constraint `n <= 2^m - 1` via a
> > BUG_ON(), where `n` is `block_size + ecc_size` and `m` is `symsize` for
>   ^^^^^^^^
> Better to provide a link, e.g. [1].
>
> [1]: https://elixir.bootlin.com/linux/v6.15/source/lib/reed_solomon/decode_rs.c#L43

You're right, I'll add that link to this `BUG_ON()` in the v2 patch.

>
> > the pstore RAM backend. A driver providing invalid parameters can trigger
> > this, leading to a kernel panic. For more details on the theory behind:
> > https://www.cs.cmu.edu/~guyb/realworld/reedsolomon/reed_solomon_codes.html
> >
> > This issue was discovered during develop chromeos_pstore driver:
>
> s/develop/developing/.

Thank you for pointing this out. I'll fix the typo in the v2 patch.

Best regards,
Naoya Tezuka