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

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Den 20.02.2017 20.40, skrev Stefan Wahren:
Hi,

Noralf Trønnes <noralf@xxxxxxxxxxx> 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@xxxxxxxxxxx>
CC: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
Reported-by: Peter Robinson <pbrobinson@xxxxxxxxx>
Fixes: e2474541032d ("bcm2835: Fix hang for writing messages larger than 16 bytes")
Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
---
   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@xxxxxxxxxxx>

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.

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