Re: [PATCH v3 9/9] bus: mhi: core: Ensure non-zero session or sequence ID values

[bbhatt]

On 2020-04-30 08:12, Jeffrey Hugo wrote:
> On 4/29/2020 2:52 PM, Bhaumik Bhatt wrote:
> > While writing any sequence or session identifiers, it is possible that
> > the host could write a zero value, whereas only non-zero values are
> > supported writes to those registers. Ensure that host does not write a
> > non-zero value for those cases.
> >
> > Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
> > ---
> >   drivers/bus/mhi/core/boot.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/bus/mhi/core/boot.c b/drivers/bus/mhi/core/boot.c
> > index 0bc9c50..c9971d4 100644
> > --- a/drivers/bus/mhi/core/boot.c
> > +++ b/drivers/bus/mhi/core/boot.c
> > @@ -199,6 +199,9 @@ static int mhi_fw_load_amss(struct mhi_controller 
> > *mhi_cntrl,
> >   	mhi_write_reg(mhi_cntrl, base, BHIE_TXVECSIZE_OFFS, mhi_buf->len);
> >     	sequence_id = prandom_u32() & BHIE_TXVECSTATUS_SEQNUM_BMSK;
> > +	if (unlikely(!sequence_id))
> > +		sequence_id = 1;
>
> Seems like you could use prandom_u32_max(), and add 1 to the result to
> eliminate the conditional.  What do you think?

Agreed. Done using an internal macro in those places.

> > +
> >   	mhi_write_reg_field(mhi_cntrl, base, BHIE_TXVECDB_OFFS,
> >   			    BHIE_TXVECDB_SEQNUM_BMSK, BHIE_TXVECDB_SEQNUM_SHFT,
> >   			    sequence_id);
> > @@ -254,6 +257,9 @@ static int mhi_fw_load_sbl(struct mhi_controller 
> > *mhi_cntrl,
> >   		      lower_32_bits(dma_addr));
> >   	mhi_write_reg(mhi_cntrl, base, BHI_IMGSIZE, size);
> >   	session_id = prandom_u32() & BHI_TXDB_SEQNUM_BMSK;
> > +	if (unlikely(!session_id))
> > +		session_id = 1;
> > +
> >   	mhi_write_reg(mhi_cntrl, base, BHI_IMGTXDB, session_id);
> >   	read_unlock_bh(pm_lock);