[PATCH RFC 1/3] i2c: bcm2835: Avoid possible NULL ptr dereference

[Noralf Trønnes]

Den 20.02.2017 20.40, skrev Stefan Wahren:
> Hi,
>
>> Noralf Trønnes <noralf at tronnes.org> hat am 18. Februar 2017 um 19:34 geschrieben:
>>
>>
>>
>> Den 16.02.2017 22.20, skrev Stefan Wahren:
>>> Since commit e2474541032d ("bcm2835: Fix hang for writing messages
>>> larger than 16 bytes") the interrupt handler is prone to a possible
>>> NULL pointer dereference. This could happen if an interrupt fires
>>> before curr_msg is set by bcm2835_i2c_xfer_msg() and randomly occurs
>>> on the RPi 3. Even this is an unexpected behavior the driver must
>>> handle that with an error instead of a crash.
>>>
>>> CC: Noralf Trønnes <noralf at tronnes.org>
>>> CC: Martin Sperl <kernel at martin.sperl.org>
>>> Reported-by: Peter Robinson <pbrobinson at gmail.com>
>>> Fixes: e2474541032d ("bcm2835: Fix hang for writing messages larger than 16 bytes")
>>> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
>>> ---
>>>    drivers/i2c/busses/i2c-bcm2835.c |    4 +++-
>>>    1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
>>> index c3436f6..10e39c8 100644
>>> --- a/drivers/i2c/busses/i2c-bcm2835.c
>>> +++ b/drivers/i2c/busses/i2c-bcm2835.c
>>> @@ -195,7 +195,9 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
>>>    	}
>>>    
>>>    	if (val & BCM2835_I2C_S_DONE) {
>>> -		if (i2c_dev->curr_msg->flags & I2C_M_RD) {
>>> +		if (!i2c_dev->curr_msg) {
>>> +			dev_err(i2c_dev->dev, "Got unexpected interrupt (from firmware?)\n");
>>> +		} else if (i2c_dev->curr_msg->flags & I2C_M_RD) {
>>>    			bcm2835_drain_rxfifo(i2c_dev);
>>>    			val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
>>>    		}
>> Thanks,
>>
>> Acked-by: Noralf Trønnes <noralf at tronnes.org>
>>
> thanks, but i would be more happier to receive feedback for patches 2 and 3.

I have only worked on dts files downstream and never done any arm64
stuff, so I'm not up to speed on this.

Noralf.