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Date:   Mon, 11 Jan 2021 14:02:20 +0800
From:   Can Guo <cang@codeaurora.org>
To:     Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com, alim.akhtar@samsung.com,
        avri.altman@wdc.com, bvanassche@acm.org,
        martin.petersen@oracle.com, stanley.chu@mediatek.com,
        Jaegeuk Kim <jaegeuk@google.com>
Subject: Re: [PATCH] scsi: ufs: should not override buffer lengh
In-Reply-To: <6551e7d6dd7dc4132dc69e77a51f6f21@codeaurora.org>
References: <20210111044443.1405049-1-jaegeuk@kernel.org>
 <6551e7d6dd7dc4132dc69e77a51f6f21@codeaurora.org>
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Sorry, typo corrected.

Hi Jaegeuk,

I think the problem is that func ufshcd_read_desc_param() is not 
expecting
one access unsupported descriptors on RPMB LU.

If we can get the right buf_len from func 
ufshcd_map_desc_id_to_length(),
the issue won't happen. - 
https://lore.kernel.org/patchwork/patch/1323421/.

What do you think if we update ufshcd_map_desc_id_to_length(add one 
param - desc_index)
so that it can tell the correct buf_len in case of RPMB LU?

Thanks,
Can Guo.

> On 2021-01-11 12:44, Jaegeuk Kim wrote:
>> From: Jaegeuk Kim <jaegeuk@google.com>
>> 
>> Kernel stack violation when getting unit_descriptor/wb_buf_alloc_units 
>> from
>> rpmb lun. The reason is the unit descriptor length is different per 
>> LU.
>> 
>> The lengh of Normal LU is 45, while the one of rpmb LU is 35.
>> 
>> int ufshcd_read_desc_param(struct ufs_hba *hba, ...)
>> {
>> 	param_offset=41;
>> 	param_size=4;
>> 	buff_len=45;
>> 	...
>> 	buff_len=35 by rpmb LU;
>> 
>> 	if (is_kmalloc) {
>> 		/* Make sure we don't copy more data than available */
>> 		if (param_offset + param_size > buff_len)
>> 			param_size = buff_len - param_offset;
>> 			--> param_size = 250;
>> 		memcpy(param_read_buf, &desc_buf[param_offset], param_size);
>> 		--> memcpy(param_read_buf, desc_buf+41, 250);
>> 
>> [  141.868974][ T9174] Kernel panic - not syncing: stack-protector:
>> Kernel stack is corrupted in: wb_buf_alloc_units_show+0x11c/0x11c
>> 	}
>> }
>> 
>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index 2a715f13fe1d..722697b57777 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -3293,8 +3293,12 @@ int ufshcd_read_desc_param(struct ufs_hba *hba,
>> 
>>  	if (is_kmalloc) {
>>  		/* Make sure we don't copy more data than available */
>> -		if (param_offset + param_size > buff_len)
>> -			param_size = buff_len - param_offset;
>> +		if (param_offset + param_size > buff_len) {
>> +			if (buff_len > param_offset)
>> +				param_size = buff_len - param_offset;
>> +			else
>> +				param_size = 0;
>> +		}
>>  		memcpy(param_read_buf, &desc_buf[param_offset], param_size);
>>  	}
>>  out: