Re: [PATCH v2 3/4][next] scsi: megaraid_sas: Replace one-element array with flexible-array member in MR_DRV_RAID_MAP

["Gustavo A. R. Silva" <gustavoars@kernel.org>]

On Wed, Jun 22, 2022 at 03:26:38PM -0700, Kees Cook wrote:
> On Wed, Aug 04, 2021 at 11:20:04PM -0500, Gustavo A. R. Silva wrote:
> > Replace one-element array with a flexible-array member in struct
> > MR_DRV_RAID_MAP and use the flex_array_size() helper.
> > 
> > This helps with the ongoing efforts to globally enable -Warray-bounds
> > and get us closer to being able to tighten the FORTIFY_SOURCE routines
> > on memcpy().
> > 
> > Link: https://en.wikipedia.org/wiki/Flexible_array_member
> > Link: https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
> > Link: https://github.com/KSPP/linux/issues/79
> > Link: https://github.com/KSPP/linux/issues/109
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> I'd really like to see this fixed. :) I'm running into this 1-element
> array problem now with UBSAN_BOUNDS:

Wow; another forgoten patch from the times we didn't have Patchwork. :) 

> 
> [   10.011173] UBSAN: array-index-out-of-bounds in /build/linux-WLUive/linux-5.15.0/drivers/scsi/megaraid/megaraid_sas_fp.c:103:32
> [   10.087824] index 1 is out of range for type 'MR_LD_SPAN_MAP [1]'
> 
> and I'm not the only one:
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=215943

It's actually great that other people are running into these issues now.
That could only means that we should fixed ASAP. :)

We also have this other series that hasn't been applied yet:

https://lore.kernel.org/linux-hardening/cover.1645513670.git.gustavoars@kernel.org/

> 
> > ---
> > Changes in v2:
> >  - None.
> > 
> >  drivers/scsi/megaraid/megaraid_sas_fp.c     | 6 +++---
> >  drivers/scsi/megaraid/megaraid_sas_fusion.h | 2 +-
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/scsi/megaraid/megaraid_sas_fp.c b/drivers/scsi/megaraid/megaraid_sas_fp.c
> > index da1cad1ee123..9cb36ef96c2c 100644
> > --- a/drivers/scsi/megaraid/megaraid_sas_fp.c
> > +++ b/drivers/scsi/megaraid/megaraid_sas_fp.c
> > @@ -229,8 +229,8 @@ static int MR_PopulateDrvRaidMap(struct megasas_instance *instance, u64 map_id)
> >  					le32_to_cpu(desc_table->raid_map_desc_offset));
> >  				memcpy(pDrvRaidMap->ldSpanMap,
> >  				       fw_map_dyn->ld_span_map,
> > -				       sizeof(struct MR_LD_SPAN_MAP) *
> > -				       le32_to_cpu(desc_table->raid_map_desc_elements));
> > +				       flex_array_size(pDrvRaidMap, ldSpanMap,
> > +				       le32_to_cpu(desc_table->raid_map_desc_elements)));
> >  			break;
> >  			default:
> >  				dev_dbg(&instance->pdev->dev, "wrong number of desctableElements %d\n",
> > @@ -254,7 +254,7 @@ static int MR_PopulateDrvRaidMap(struct megasas_instance *instance, u64 map_id)
> >  			pDrvRaidMap->ldTgtIdToLd[i] =
> >  				(u16)fw_map_ext->ldTgtIdToLd[i];
> >  		memcpy(pDrvRaidMap->ldSpanMap, fw_map_ext->ldSpanMap,
> > -		       sizeof(struct MR_LD_SPAN_MAP) * ld_count);
> > +		       flex_array_size(pDrvRaidMap, ldSpanMap, ld_count));
> >  		memcpy(pDrvRaidMap->arMapInfo, fw_map_ext->arMapInfo,
> >  		       sizeof(struct MR_ARRAY_INFO) * MAX_API_ARRAYS_EXT);
> >  		memcpy(pDrvRaidMap->devHndlInfo, fw_map_ext->devHndlInfo,
> > diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.h b/drivers/scsi/megaraid/megaraid_sas_fusion.h
> > index 9adb8b30f422..5fe2f7a6eebe 100644
> > --- a/drivers/scsi/megaraid/megaraid_sas_fusion.h
> > +++ b/drivers/scsi/megaraid/megaraid_sas_fusion.h
> > @@ -1182,7 +1182,7 @@ struct MR_DRV_RAID_MAP {
> >  		devHndlInfo[MAX_RAIDMAP_PHYSICAL_DEVICES_DYN];
> >  	u16 ldTgtIdToLd[MAX_LOGICAL_DRIVES_DYN];
> >  	struct MR_ARRAY_INFO arMapInfo[MAX_API_ARRAYS_DYN];
> > -	struct MR_LD_SPAN_MAP      ldSpanMap[1];
> > +	struct MR_LD_SPAN_MAP      ldSpanMap[];
> >  
> >  };
> >  
> 
> I think this patch is incomplete, and the wrapping struct needs to be
> adjusted too:
> 
> @@ -1193,7 +1193,7 @@ struct MR_DRV_RAID_MAP {
>  struct MR_DRV_RAID_MAP_ALL {
>  
>         struct MR_DRV_RAID_MAP raidMap;
> -       struct MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES_DYN - 1];
> +       struct MR_LD_SPAN_MAP ldSpanMap[MAX_LOGICAL_DRIVES_DYN];
>  } __packed;
>  
> With that added, I get zero changes to the executable code.
> 
> I assume the others need adjustment too.

Interesting... OK, let me refresh my memory about the whole thing
and be back in a minute.

--
Gustavo