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

[Jeffrey Hugo <quic_jhugo@quicinc.com>]

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?

> 
>> Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
>> Reviewed-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.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?

> 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
>>
>>
>