Re: [PATCH mtd-utils] nand-utils: Fix integer overflow in nandflipbits.c

[Zhihao Cheng <chengzhihao1@huawei.com>]

在 2024/12/18 0:36, Anton Moryakov 写道:
> Report of the static analyzer:
> The value of an arithmetic expression 'page * (mtd.min_io_size + mtd.oob_size)' is a subject to overflow because its operands are not cast to a larger data type before performing arithmetic
> 
> Corrections explained:
> Casting bit_to_flip->block to unsigned long long expands the range of values ​​and allows the result of the multiplication to be calculated in a wider data type.
> The arithmetic is performed in a safe range, preventing overflow.
> Sum + blkoffs is now also safe, since the result of the expression is already calculated in unsigned long long.
> 
> Triggers found by static analyzer Svace.
> 
> Signed-off-by: Anton Moryakov <ant.v.moryakov@gmail.com>
> 
> ---
>   nand-utils/nandflipbits.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/nand-utils/nandflipbits.c b/nand-utils/nandflipbits.c
> index ef663c6..c4642fe 100644
> --- a/nand-utils/nandflipbits.c
> +++ b/nand-utils/nandflipbits.c
> @@ -213,7 +213,7 @@ int main(int argc, char **argv)
>   		bits_to_flip[i].block = bits_to_flip[i].offset / blklen;
>   		bits_to_flip[i].offset %= blklen;
>   		page = bits_to_flip[i].offset / pagelen;
> -		bits_to_flip[i].offset = (page *
> +		bits_to_flip[i].offset = ((unsigned long long)page *
>   					  (mtd.min_io_size + mtd.oob_size)) +
>   					 (bits_to_flip[i].offset % pagelen);

I think the 'bits_to_flip[i].offset' is limited smaller than 
'mtd.eb_size' by the code:
  bits_to_flip[i].offset %= blklen;
  page = bits_to_flip[i].offset / pagelen;
So, I don't think an overflow could happen here.
>   	}
> 


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