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Message-ID: <20230522102953.2fdf2b02@xps-13>
Date: Mon, 22 May 2023 10:29:53 +0200
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: richard@....at, todd.e.brandt@...el.com, vigneshr@...com,
pratyush@...nel.org, michael@...le.cc,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
regressions@...mhuis.info, bagasdotme@...il.com,
regressions@...ts.linux.dev, joneslee@...gle.com,
Todd Brandt <todd.e.brandt@...ux.intel.com>
Subject: Re: [PATCH] mtd: spi-nor: Fix divide by zero for spi-nor-generic
flashes
Hi Tudor,
tudor.ambarus@...aro.org wrote on Thu, 18 May 2023 08:54:40 +0000:
> We failed to initialize n_banks for spi-nor-generic flashes, which
> caused a devide by zero when computing the bank_size.
>
> By default we consider that all chips have a single bank. Initialize
> the default number of banks for spi-nor-generic flashes. Even if the
> bug is fixed with this simple initialization, check the n_banks value
> before dividing so that we make sure this kind of bug won't occur again
> if some other struct instance is created uninitialized.
>
> Suggested-by: Todd Brandt <todd.e.brandt@...ux.intel.com>
> Reported-by: Todd Brandt <todd.e.brandt@...ux.intel.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217448
> Fixes: 9d6c5d64f028 ("mtd: spi-nor: Introduce the concept of bank")
> Link: https://lore.kernel.org/all/20230516225108.29194-1-todd.e.brandt@intel.com/
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---
> drivers/mtd/spi-nor/core.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 0bb0ad14a2fc..5f29fac8669a 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2018,6 +2018,7 @@ static const struct spi_nor_manufacturer *manufacturers[] = {
>
> static const struct flash_info spi_nor_generic_flash = {
> .name = "spi-nor-generic",
> + .n_banks = 1,
I definitely missed that structure.
> /*
> * JESD216 rev A doesn't specify the page size, therefore we need a
> * sane default.
> @@ -2921,7 +2922,8 @@ static void spi_nor_late_init_params(struct spi_nor *nor)
> if (nor->flags & SNOR_F_HAS_LOCK && !nor->params->locking_ops)
> spi_nor_init_default_locking_ops(nor);
>
> - nor->params->bank_size = div64_u64(nor->params->size, nor->info->n_banks);
> + if (nor->info->n_banks > 1)
> + params->bank_size = div64_u64(params->size, nor->info->n_banks);
I'm fine with the check as it is written because it also look like an
optimization, but bank_size should never be 0 otherwise it's a real bug
that must be catch and fixed. We do not want uninitialized bank_size's.
> }
>
> /**
> @@ -2987,6 +2989,7 @@ static void spi_nor_init_default_params(struct spi_nor *nor)
> /* Set SPI NOR sizes. */
> params->writesize = 1;
> params->size = (u64)info->sector_size * info->n_sectors;
> + params->bank_size = params->size;
> params->page_size = info->page_size;
We actually discarded that line in a previous discussion:
https://lore.kernel.org/linux-mtd/20230331194620.839899-1-miquel.raynal@bootlin.com/T/#mcb4f90f7ca48ffe3d9838b2ac6f74e44460c51bd
I'm fine to re-add it though, it does not hurt.
>
> if (!(info->flags & SPI_NOR_NO_FR)) {
Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>
Thanks,
Miquèl
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