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

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Date:   Tue, 27 Sep 2022 09:23:17 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Yu Zhe <yuzhe@...china.com>
CC:     "Schofield, Alison" <alison.schofield@...el.com>,
        "Verma, Vishal L" <vishal.l.verma@...el.com>,
        "bwidawsk@...nel.org" <bwidawsk@...nel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "liqiong@...china.com" <liqiong@...china.com>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH] cxl/pmem: Use size_add() against integer overflow

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@...china.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
>