power: supply: sbs-battery: Fix use-after-free in power_supply_changed()

Using the `devm_` variant for requesting IRQ _before_ the `devm_`
variant for allocating/registering the `power_supply` handle, means that
the `power_supply` handle will be deallocated/unregistered _before_ the
interrupt handler (since `devm_` naturally deallocates in reverse
allocation order). This means that during removal, there is a race
condition where an interrupt can fire just _after_ the `power_supply`
handle has been freed, *but* just _before_ the corresponding
unregistration of the IRQ handler has run.

This will lead to the IRQ handler calling `power_supply_changed()` with
a freed `power_supply` handle. Which usually crashes the system or
otherwise silently corrupts the memory...

Note that there is a similar situation which can also happen during
`probe()`; the possibility of an interrupt firing _before_ registering
the `power_supply` handle. This would then lead to the nasty situation
of using the `power_supply` handle *uninitialized* in
`power_supply_changed()`.

Fix this racy use-after-free by making sure the IRQ is requested _after_
the registration of the `power_supply` handle. Keep the old behavior of
just printing a warning in case of any failures during the IRQ request
and finishing the probe successfully.

Fixes: d2cec82c2880 ("power: sbs-battery: Request threaded irq and fix dev callback cookie")
Signed-off-by: Waqar Hameed <waqar.hameed@axis.com>
Reviewed-by: Phil Reid <preid@electromag.com.au>
Link: https://patch.msgid.link/0ef896e002495e615157b482d18a437af19ddcd0.1766268280.git.waqar.hameed@axis.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

diff --git a/drivers/power/supply/sbs-battery.c b/drivers/power/supply/sbs-battery.c
index 943c82ee978f40abd2b1f2ecd4850cf3b41fd446..43c48196c167415c9a055e68fcaa8b5e465994b0 100644 (file)
--- a/drivers/power/supply/sbs-battery.c
+++ b/drivers/power/supply/sbs-battery.c
@@ -1174,24 +1174,6 @@ static int sbs_probe(struct i2c_client *client)
 
        i2c_set_clientdata(client, chip);
 
-       if (!chip->gpio_detect)
-               goto skip_gpio;
-
-       irq = gpiod_to_irq(chip->gpio_detect);
-       if (irq <= 0) {
-               dev_warn(&client->dev, "Failed to get gpio as irq: %d\n", irq);
-               goto skip_gpio;
-       }
-
-       rc = devm_request_threaded_irq(&client->dev, irq, NULL, sbs_irq,
-               IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
-               dev_name(&client->dev), chip);
-       if (rc) {
-               dev_warn(&client->dev, "Failed to request irq: %d\n", rc);
-               goto skip_gpio;
-       }
-
-skip_gpio:
        /*
         * Before we register, we might need to make sure we can actually talk
         * to the battery.
@@ -1217,6 +1199,24 @@ skip_gpio:
                return dev_err_probe(&client->dev, PTR_ERR(chip->power_supply),
                                     "Failed to register power supply\n");
 
+       if (!chip->gpio_detect)
+               goto out;
+
+       irq = gpiod_to_irq(chip->gpio_detect);
+       if (irq <= 0) {
+               dev_warn(&client->dev, "Failed to get gpio as irq: %d\n", irq);
+               goto out;
+       }
+
+       rc = devm_request_threaded_irq(&client->dev, irq, NULL, sbs_irq,
+               IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+               dev_name(&client->dev), chip);
+       if (rc) {
+               dev_warn(&client->dev, "Failed to request irq: %d\n", rc);
+               goto out;
+       }
+
+out:
        dev_info(&client->dev,
                "%s: battery gas gauge device registered\n", client->name);