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

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Date:   Wed, 16 Mar 2022 07:47:40 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <Alexander.Stein@...group.com>, <linux-mtd@...ts.infradead.org>
CC:     <michael@...le.cc>, <p.yadav@...com>, <vigneshr@...com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mtd: spi-nor: Fix shift-out-of-bounds

On 3/16/22 09:39, Alexander Stein wrote:
> [You don't often get email from alexander.stein@...group.com. Learn why this is important at http://aka.ms/LearnAboutSenderIdentification.]
> 
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> 
> Hello,

hi,

> 
> Am Samstag, 6. November 2021, 08:56:15 CET 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;
>> +     }
>>  }
>>
>>  /**
> 
> What is the status of this patch? It is not applied up until now, no? Has it
> been superseeded?
> 

I think it's marked with "changes requested". I'm going to send a v2.