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Subject: Re: [PATCH] cxl/pmem: Use size_add() against integer overflow
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     "Schofield, Alison" <alison.schofield@intel.com>,
        "Verma, Vishal L" <vishal.l.verma@intel.com>,
        "bwidawsk@kernel.org" <bwidawsk@kernel.org>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        "linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "liqiong@nfschina.com" <liqiong@nfschina.com>,
        "kernel-janitors@vger.kernel.org" <kernel-janitors@vger.kernel.org>
References: <20220927070247.23148-1-yuzhe@nfschina.com>
 <YzMjdXArM28bDsQf@iweiny-desk3>
From:   Yu Zhe <yuzhe@nfschina.com>
Message-ID: <eeec4e7f-01e1-a601-f89e-3dfa2611b039@nfschina.com>
Date:   Thu, 29 Sep 2022 15:02:47 +0800
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在 2022年09月28日 00:23, Ira Weiny 写道:

> 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?
"struct_size() + 4" still might cause overflow, so there need to use 
"size_add" to check it.
> Were you able to get this to fail with some user input?
>
> Ira
>
>>   		return -EINVAL;
>>   
>>   	set_lsa =
>> -- 
>> 2.11.0
>>
>>