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@xxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > ---
> >  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: