diff options
authorVincent Whitchurch <vincent.whitchurch@axis.com>2018-08-31 09:04:18 +0200
committerLinus Walleij <linus.walleij@linaro.org>2018-08-31 11:30:45 +0200
commitd49b48f088c323dbacae44dfbe56d9c985c8a2a1 (patch)
parenta618cf4800970d260871c159b7eec014a1da2e81 (diff)
gpio: Fix crash due to registration racegpio-v4.19-2
gpiochip_add_data_with_key() adds the gpiochip to the gpio_devices list before of_gpiochip_add() is called, but it's only the latter which sets the ->of_xlate function pointer. gpiochip_find() can be called by someone else between these two actions, and it can find the chip and call of_gpiochip_match_node_and_xlate() which leads to the following crash due to a NULL ->of_xlate(). Unhandled prefetch abort: page domain fault (0x01b) at 0x00000000 Modules linked in: leds_gpio(+) gpio_generic(+) CPU: 0 PID: 830 Comm: insmod Not tainted 4.18.0+ #43 Hardware name: ARM-Versatile Express PC is at (null) LR is at of_gpiochip_match_node_and_xlate+0x2c/0x38 Process insmod (pid: 830, stack limit = 0x(ptrval)) (of_gpiochip_match_node_and_xlate) from (gpiochip_find+0x48/0x84) (gpiochip_find) from (of_get_named_gpiod_flags+0xa8/0x238) (of_get_named_gpiod_flags) from (gpiod_get_from_of_node+0x2c/0xc8) (gpiod_get_from_of_node) from (devm_fwnode_get_index_gpiod_from_child+0xb8/0x144) (devm_fwnode_get_index_gpiod_from_child) from (gpio_led_probe+0x208/0x3c4 [leds_gpio]) (gpio_led_probe [leds_gpio]) from (platform_drv_probe+0x48/0x9c) (platform_drv_probe) from (really_probe+0x1d0/0x3d4) (really_probe) from (driver_probe_device+0x78/0x1c0) (driver_probe_device) from (__driver_attach+0x120/0x13c) (__driver_attach) from (bus_for_each_dev+0x68/0xb4) (bus_for_each_dev) from (bus_add_driver+0x1a8/0x268) (bus_add_driver) from (driver_register+0x78/0x10c) (driver_register) from (do_one_initcall+0x54/0x1fc) (do_one_initcall) from (do_init_module+0x64/0x1f4) (do_init_module) from (load_module+0x2198/0x26ac) (load_module) from (sys_finit_module+0xe0/0x110) (sys_finit_module) from (ret_fast_syscall+0x0/0x54) One way to fix this would be to rework the hairy registration sequence in gpiochip_add_data_with_key(), but since I'd probably introduce a couple of new bugs if I attempted that, simply add a check for a non-NULL of_xlate function pointer in of_gpiochip_match_node_and_xlate(). This works since the driver looking for the gpio will simply fail to find the gpio and defer its probe and be reprobed when the driver which is registering the gpiochip has fully completed its probe. Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index a4f1157d6aa0..d4e7a09598fa 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -31,6 +31,7 @@ static int of_gpiochip_match_node_and_xlate(struct gpio_chip *chip, void *data)
struct of_phandle_args *gpiospec = data;
return chip->gpiodev->dev.of_node == gpiospec->np &&
+ chip->of_xlate &&
chip->of_xlate(chip, gpiospec, NULL) >= 0;

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