[PATCH] scsi: ufs: should not override buffer lengh

[PATCH] scsi: ufs: should not override buffer lengh

[Jaegeuk Kim]

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:
-- 
2.30.0.284.gd98b1dd5eaa7-goog

Re: [PATCH] scsi: ufs: should not override buffer lengh

[Can Guo]

Hi Jaegeuk,

I think the problem is that func ufshcd_read_desc_param() is not 
expecting
one access unsupported descriptors on all W-LUs, not just 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 W-LUs?

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:

Re: [PATCH] scsi: ufs: should not override buffer lengh

[Can Guo]

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:

RE: [PATCH] scsi: ufs: should not override buffer lengh

[Avri Altman]

> 
> 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.
Correct.
This is about wb introducing a new constraint: wb buffer is only allowed in lu 0..7.
And this is why, IMHO, the fix should be in ufs_is_valid_unit_desc_lun,
To include param offset, as it is only called in contingency of ufshcd_read_desc_param.

Thanks,
Avri

Re: [PATCH] scsi: ufs: should not override buffer lengh

[Can Guo]

On 2021-01-11 16:15, Avri Altman wrote:
>> 
>> 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.
> Correct.
> This is about wb introducing a new constraint: wb buffer is only
> allowed in lu 0..7.
> And this is why, IMHO, the fix should be in ufs_is_valid_unit_desc_lun,
> To include param offset, as it is only called in contingency of
> ufshcd_read_desc_param.
> 
> Thanks,
> Avri

Yeah... Fixing it in ufs-sysfs.c also works. Anyways, the math in
ufshcd_read_desc_param is already complex. Let's fix it somewhere
close to the source/initiator.

Thanks,
Can Guo.

Re: [PATCH] scsi: ufs: should not override buffer lengh

[Jaegeuk Kim]

On 01/11, Can Guo wrote:
> On 2021-01-11 16:15, Avri Altman wrote:
> > > 
> > > 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.
> > Correct.
> > This is about wb introducing a new constraint: wb buffer is only
> > allowed in lu 0..7.
> > And this is why, IMHO, the fix should be in ufs_is_valid_unit_desc_lun,
> > To include param offset, as it is only called in contingency of
> > ufshcd_read_desc_param.
> > 
> > Thanks,
> > Avri
> 
> Yeah... Fixing it in ufs-sysfs.c also works. Anyways, the math in
> ufshcd_read_desc_param is already complex. Let's fix it somewhere
> close to the source/initiator.

Thank you, Can and Avri.
I think fixing the lun check makese sense. Let me post v2. :)

> 
> Thanks,
> Can Guo.