Re: [PATCH] cxl/pmem: Use size_add() against integer overflow

[Ira Weiny <ira.weiny@intel.com>]

On Tue, Sep 27, 2022 at 12:02:47AM -0700, Yu Zhe wrote:
> "struct_size() + n" may cause a integer overflow,
> use size_add() to handle it.
> 
> Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
> ---
>  drivers/cxl/pmem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index 7dc0a2fa1a6b..8c08aa009a56 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -148,7 +148,7 @@ static int cxl_pmem_set_config_data(struct cxl_dev_state *cxlds,
>  		return -EINVAL;
>  
>  	/* 4-byte status follows the input data in the payload */
> -	if (struct_size(cmd, in_buf, cmd->in_length) + 4 > buf_len)
> +	if (size_add(struct_size(cmd, in_buf, cmd->in_length), 4) > buf_len)

I don't see any benefit here.

struct_size() calls __ab_c_size() which already calls check_add_overflow()?  So
why wrap that in another check?

Were you able to get this to fail with some user input?

Ira

>  		return -EINVAL;
>  
>  	set_lsa =
> -- 
> 2.11.0
>