On 15/03/22 4:30 pm, Andy Shevchenko wrote:
On Tue, Mar 15, 2022 at 12:38 PM Shreeya Patel
<shreeya.patel@xxxxxxxxxxxxx> wrote:
Thanks for the update, my comments below.
gc irq members are exposed before they could be completely
gc --> GPIO chip
initialized and this leads to race conditions.
Any example here. like ~3-4 lines of the Oops in question?
One such issue was observed for the gc->irq.domain variable which
was accessed through the I2C interface in gpiochip_to_irq() before
it could be initialized by gpiochip_add_irqchip(). This resulted in
Kernel NULL pointer dereference.
To avoid such scenarios, restrict usage of gc irq members before
gc --> GPIO chip
they are completely initialized.
...
+ /*
+ * Using barrier() here to prevent compiler from reordering
+ * gc->irq.gc_irq_initialized before initialization of above
+ * gc irq members.
+ */
+ barrier();
+
+ gc->irq.gc_irq_initialized = true;
There are too many duplications. Why not simply call it 'initialized'?
- if (gc->to_irq) {
+ if (gc->to_irq && gc->irq.gc_irq_initialized) {
Why can't this check be added into gpiochip_to_irq() ?
if (!gc->irq.initialized)
return -ENXIO;
...
Because we don't want to return -ENXIO in case of race condition.
It should return -EPROBE_DEFER similar to how we are doing when gc->to_irq
is NULL.
So in this case when both gc->to_irq = NULL and gc->irq.initialized = FALSE,
we will be returning -EPROBE_DEFER. This will make sure that devices
like touchscreen
do not become fatal due to returning -ENXIO.
+ bool gc_irq_initialized;
Can you move it closer to .init_hw so it will be weakly grouped by
logic similarities?
Also see above.
Thanks for your comments, I'll make the necessary changes and send a v3.
Shreeya Patel
