linux-kernel - Re: [PATCH v4] mtd: cfi_cmdset

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Date:   Fri, 27 Oct 2023 19:47:11 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Nicolas Pitre <nico@...xnic.net>
Subject: Re: [PATCH v4] mtd: cfi_cmdset_0001: Byte swap OTP info

On Fri, 2023-10-20 at 20:30:29 UTC, Linus Walleij wrote:
> Currently the offset into the device when looking for OTP
> bits can go outside of the address of the MTD NOR devices,
> and if that memory isn't readable, bad things happen
> on the IXP4xx (added prints that illustrate the problem before
> the crash):
> 
> cfi_intelext_otp_walk walk OTP on chip 0 start at reg_prot_offset 0x00000100
> ixp4xx_copy_from copy from 0x00000100 to 0xc880dd78
> cfi_intelext_otp_walk walk OTP on chip 0 start at reg_prot_offset 0x12000000
> ixp4xx_copy_from copy from 0x12000000 to 0xc880dd78
> 8<--- cut here ---
> Unable to handle kernel paging request at virtual address db000000
> [db000000] *pgd=00000000
> (...)
> 
> This happens in this case because the IXP4xx is big endian and
> the 32- and 16-bit fields in the struct cfi_intelext_otpinfo are not
> properly byteswapped. Compare to how the code in read_pri_intelext()
> byteswaps the fields in struct cfi_pri_intelext.
> 
> Adding a small byte swapping loop for the OTP in read_pri_intelext()
> and the crash goes away.
> 
> The problem went unnoticed for many years until I enabled
> CONFIG_MTD_OTP on the IXP4xx as well, triggering the bug.
> 
> Cc: stable@...r.kernel.org
> Reviewed-by: Nicolas Pitre <nico@...xnic.net>
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel