linux-kernel - Re: (EXT) [PATCH 1/2] mtd: spi-nor: Fix shift-out-of-bounds

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Date:   Mon, 8 Nov 2021 09:26:49 +0000
From:   "Stein, Alexander" <Alexander.Stein@...group.com>
To:     "p.yadav@...com" <p.yadav@...com>,
        "vigneshr@...com" <vigneshr@...com>,
        "michael@...le.cc" <michael@...le.cc>,
        "tudor.ambarus@...rochip.com" <tudor.ambarus@...rochip.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>
Subject: Re: (EXT) [PATCH 1/2] mtd: spi-nor: Fix shift-out-of-bounds



Am Samstag, dem 06.11.2021 um 09:56 +0200 schrieb Tudor Ambarus:
> When paring SFDP we may choose to mask out an erase type, passing
> an erase size of zero to spi_nor_set_erase_type().
> Fix shift-out-of-bounds and just clear the erase params when
> passing zero for erase size.
> While here avoid a superfluous dereference and use 'size' directly.
> 
> UBSAN: shift-out-of-bounds in drivers/mtd/spi-nor/core.c:2237:24
> shift exponent 4294967295 is too large for 32-bit type 'int'
> 
> Fixes: 5390a8df769e ("mtd: spi-nor: add support to non-uniform SFDP
> SPI NOR flash memories")
> Reported-by: Alexander Stein <
> Alexander.Stein@...group.com
> >
> Signed-off-by: Tudor Ambarus <
> tudor.ambarus@...rochip.com
> >
> ---
>  drivers/mtd/spi-nor/core.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 3d97c189c332..a1b5d5432f41 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2230,8 +2230,13 @@ void spi_nor_set_erase_type(struct
> spi_nor_erase_type *erase, u32 size,
>  	erase->size = size;
>  	erase->opcode = opcode;
>  	/* JEDEC JESD216B Standard imposes erase sizes to be power of
> 2. */
> -	erase->size_shift = ffs(erase->size) - 1;
> -	erase->size_mask = (1 << erase->size_shift) - 1;
> +	if (size) {
> +		erase->size_shift = ffs(size) - 1;
> +		erase->size_mask = (1 << erase->size_shift) - 1;
> +	} else {
> +		erase->size_shift = 0;
> +		erase->size_mask = 0;
> +	}
>  }
>  
>  /**

Tested-By: Alexander Stein <Alexander.Stein@...group.com>

It fixes the UBSAN error and my spi-nor flash can still be detected.

Best regards,
Alexander