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

[Can Guo <cang@codeaurora.org>]

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: