linux-kernel - Re: [PATCH] bus: mhi: host: Range check CHDBOFF and ERDBOFF

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Date:   Fri, 24 Mar 2023 19:52:55 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Jeffrey Hugo <quic_jhugo@...cinc.com>
Cc:     mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bus: mhi: host: Range check CHDBOFF and ERDBOFF

On Fri, Mar 24, 2023 at 07:50:01AM -0600, Jeffrey Hugo wrote:
> On 3/24/2023 4:34 AM, Manivannan Sadhasivam wrote:
> > On Fri, Mar 17, 2023 at 09:14:19AM -0600, Jeffrey Hugo wrote:
> > > If the value read from the CHDBOFF and ERDBOFF registers is outside the
> > > range of the MHI register space then an invalid address might be computed
> > > which later causes a kernel panic.  Range check the read value to prevent
> > > a crash due to bad data from the device.
> > > 
> > > Fixes: 6cd330ae76ff ("bus: mhi: core: Add support for ringing channel/event ring doorbells")
> > 
> > Please CC stable list.
> 
> The stable folks have been automatically picking up everything with a fixes
> tag for years.  CCing the stable list does not seem to do anything unless
> the patch needs specific backporting adjustments.
> 
> Do you still want an explicit CC?
> 

That was the impression I had but Greg wanted us to explicitly CC stable list
and add a hint about how deep the patch needs to be applied.

> > 
> > > Signed-off-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
> > > Reviewed-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>
> > > ---
> > >   drivers/bus/mhi/host/init.c | 12 ++++++++++++
> > >   1 file changed, 12 insertions(+)
> > > 
> > > diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
> > > index 3d779ee..ae8ebcfb 100644
> > > --- a/drivers/bus/mhi/host/init.c
> > > +++ b/drivers/bus/mhi/host/init.c
> > > @@ -516,6 +516,12 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
> > >   		return -EIO;
> > >   	}
> > > +	if (val >= mhi_cntrl->reg_len - (8 * MHI_DEV_WAKE_DB)) {
> > > +		dev_err(dev, "CHDB offset: 0x%x is out of range: 0x%zx\n",
> > > +			val, mhi_cntrl->reg_len - (8 * MHI_DEV_WAKE_DB));
> > > +		return -EINVAL;
> > 
> > Isn't -ERANGE a better errno here and also in other places of the driver?
> 
> I suppose that could work.  This was modeled after the existing BHI (eg
> BHIOFF) range checks.  You want those updated in the same change or a
> separate one?
> 

That can go into a separate change.

Thanks,
Mani

> > Thanks,
> > Mani
> > 
> > > +	}
> > > +
> > >   	/* Setup wake db */
> > >   	mhi_cntrl->wake_db = base + val + (8 * MHI_DEV_WAKE_DB);
> > >   	mhi_cntrl->wake_set = false;
> > > @@ -532,6 +538,12 @@ int mhi_init_mmio(struct mhi_controller *mhi_cntrl)
> > >   		return -EIO;
> > >   	}
> > > +	if (val >= mhi_cntrl->reg_len - (8 * mhi_cntrl->total_ev_rings)) {
> > > +		dev_err(dev, "ERDB offset: 0x%x is out of range: 0x%zx\n",
> > > +			val, mhi_cntrl->reg_len - (8 * mhi_cntrl->total_ev_rings));
> > > +		return -EINVAL;
> > > +	}
> > > +
> > >   	/* Setup event db address for each ev_ring */
> > >   	mhi_event = mhi_cntrl->mhi_event;
> > >   	for (i = 0; i < mhi_cntrl->total_ev_rings; i++, val += 8, mhi_event++) {
> > > -- 
> > > 2.7.4
> > > 
> > > 
> > 
> 

-- 
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