Re: [PATCH] mtd: spi-nor: fix shift-out-of-bounds in spi_nor_set_erase_type()

From: Tudor Ambarus <tudor.ambarus@linaro.org>
To: Andrea Righi <andrea.righi@canonical.com>,
	Pratyush Yadav <pratyush@kernel.org>
Cc: Michael Walle <michael@walle.cc>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Cristian Birsan <cristian.birsan@microchip.com>,
	Boris Brezillon <bbrezillon@kernel.org>,
	Emil Renner Berthing <emil.renner.berthing@canonical.com>,
	linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: spi-nor: fix shift-out-of-bounds in spi_nor_set_erase_type()
Date: Wed, 22 Feb 2023 14:50:42 +0000	[thread overview]
Message-ID: <d87efbd8-5290-b462-beb3-c2d3be267ade@linaro.org> (raw)
In-Reply-To: <20230221111346.34268-1-andrea.righi@canonical.com>

Hi!

This should be fixed by:
https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git/commit/?h=spi-nor/next&id=f0f0cfdc3a024e21161714f2e05f0df3b84d42ad

Which base did you use?

Cheers,
ta

On 2/21/23 11:13, Andrea Righi wrote:
> It seems that according to JEDEC JESD216B Standard erase size needs to
> be a power of 2, but sometimes we set the size to 0 (e.g., in
> spi_nor_parse_4bait()) causing UBSAN warnings like the following:
> 
>    UBSAN: shift-out-of-bounds in drivers/mtd/spi-nor/core.c:2026:24
>    shift exponent 4294967295 is too large for 32-bit type 'int'
>    Hardware name: Dell Inc. XPS 13 9300/077Y9N, BIOS 1.11.0 03/22/2022
>    Call Trace:
>     <TASK>
>     show_stack+0x4e/0x61
>     dump_stack_lvl+0x4a/0x6f
>     dump_stack+0x10/0x18
>     ubsan_epilogue+0x9/0x3a
>     __ubsan_handle_shift_out_of_bounds.cold+0x61/0xef
>     spi_nor_set_erase_type.cold+0x16/0x1e [spi_nor]
>     spi_nor_parse_4bait+0x270/0x380 [spi_nor]
>     spi_nor_parse_sfdp+0x47f/0x610 [spi_nor]
> 
> Fix by checking if size is a power when setting struct
> spi_nor_erase_type, otherwise consider size, mask and shift as invalid.
> 
> Fixes: 5390a8df769e ("mtd: spi-nor: add support to non-uniform SFDP SPI NOR flash memories")
> Reported-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
> Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
> ---
>   drivers/mtd/spi-nor/core.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index d67c926bca8b..3c5b5bf9cbd1 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2019,11 +2019,17 @@ spi_nor_spimem_adjust_hwcaps(struct spi_nor *nor, u32 *hwcaps)
>   void spi_nor_set_erase_type(struct spi_nor_erase_type *erase, u32 size,
>   			    u8 opcode)
>   {
> -	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 (likely(is_power_of_2(size))) {
> +		erase->size = size;
> +		erase->size_shift = ffs(erase->size) - 1;
> +		erase->size_mask = (1 << erase->size_shift) - 1;
> +	} else {
> +		erase->size = 0u;
> +		erase->size_shift = ~0u;
> +		erase->size_mask = ~0u;
> +	}
>   }
>   
>   /**

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