Re: [PATCH RFC 07/15] arm_mpam: Fix the RIS index range check in mpam_ris_create_locked

[Yin Li]

On 9/2/2026 10:50 PM, Andre Przywara wrote:
> Hi,
>
> On 8/11/26 15:30, Yin Li wrote:
> > The RIS selector field is defined as MPAMCFG_PART_SEL_RIS (bits 27:24),
> > which is 4 bits wide and gives valid indices 0..15. MPAM_MSC_MAX_NUM_RIS
> > is defined as 16, so the check should use >= to reject index 16 and
> > above. The previous > check incorrectly accepted index 16 as valid.
>
> Indeed. Either the maintainers pick this one independently, or put it up 
> front in any repost.
>
> And add:
> Fixes: 01fb4b822472 ("arm_mpam: Add the class and component structures 
> for firmware described ris")
>
> > Signed-off-by: Yin Li <yin.li@xxxxxxxxxxxxxxxx>
>
> Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>

Hi Andre,

Thanks for the review and the Reviewed-by tag.

Agreed — this is an independent fix to existing code, so I'll move it to
the front of the series in the next repost and add the Fixes tag.

> Cheers,
> Andre
>
> > ---
> >   drivers/resctrl/mpam_devices.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/ 
> > mpam_devices.c
> > index ddc15249ec1e..cc9fa1d78925 100644
> > --- a/drivers/resctrl/mpam_devices.c
> > +++ b/drivers/resctrl/mpam_devices.c
> > @@ -725,7 +725,7 @@ static int mpam_ris_create_locked(struct mpam_msc 
> > *msc, u8 ris_idx,
> >       lockdep_assert_held(&mpam_list_lock);
> > -    if (ris_idx > MPAM_MSC_MAX_NUM_RIS)
> > +    if (ris_idx >= MPAM_MSC_MAX_NUM_RIS)
> >           return -EINVAL;
> >       if (test_and_set_bit(ris_idx, &msc->ris_idxs))

--
Thx and BRs,
Yin