Re: [PATCH] gpiolib: fix OOB access in quirk callbacks

[<Conor.Dooley@xxxxxxxxxxxxx>]

On 16/09/2022 12:01, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Commit a2b5e207cade ("gpiolib: rework quirk handling in of_find_gpio()")
> introduced an array of quirk functions which get iterated over. But a
> sentinal value is missing. Add it.
> 
> Fixes: a2b5e207cade ("gpiolib: rework quirk handling in of_find_gpio()")
> Signed-off-by: Michael Walle <michael@xxxxxxxx>

Tested-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

> ---
> FWIW here is the kernel oops backtrace:
> [    4.108706] Internal error: SP/PC alignment exception: 8a000000 [#1] SMP
> [    4.115470] Modules linked in:
> [    4.118549] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.0.0-rc5-next-20220916-00091-g6cae0fcbd5e7 #1821
> [    4.128033] Hardware name: Kontron KBox A-230-LS (DT)
> [    4.133127] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [    4.140154] pc : 0x61722d6f697067
> [    4.143495] lr : of_find_gpio+0x138/0x174
> [    4.147546] sp : ffff80000a24b680
> [    4.150884] x29: ffff80000a24b680 x28: 0000000000000000 x27: ffff80000996044c
> [    4.158090] x26: 0000000000000001 x25: ffff80000970f588 x24: ffff800009297968
> [    4.165295] x23: ffff80000a24b770 x22: 0000000000000000 x21: ffff0020009a7010
> [    4.172500] x20: ffff8000097752f8 x19: fffffffffffffffe x18: 0000000000000000
> [    4.179703] x17: ffff8000085fb9d0 x16: ffff8000085fb264 x15: ffff8000085f96ac
> [    4.186907] x14: 0000000000000000 x13: ffff80000884b3e8 x12: ffff80000884ab04
> [    4.194111] x11: ffff80000884aa54 x10: 0000000000025080 x9 : ffff8000085fce78
> [    4.201316] x8 : 0101010101010101 x7 : ffff800009750268 x6 : 051f521459491b57
> [    4.208520] x5 : 571b495914521f05 x4 : 6e61722d6f697067 x3 : ffff80000a24b6d4
> [    4.215724] x2 : 0000000000000000 x1 : ffff8000097752f8 x0 : ffff00207f7e4b20
> [    4.222928] Call trace:
> [    4.225389]  0x61722d6f697067
> [    4.228377]  gpiod_get_index+0x12c/0x440
> [    4.232334]  devm_gpiod_get_index+0x34/0xf0
> [    4.236553]  devm_gpiod_get_optional+0x20/0x40
> [    4.241036]  uart_get_rs485_mode+0x104/0x180
> [    4.245345]  serial8250_register_8250_port+0x198/0x484
> [    4.250532]  of_platform_serial_probe+0x358/0x640
> [    4.255279]  platform_probe+0x70/0xe0
> [    4.258973]  really_probe+0xc4/0x2e4
> [    4.262577]  __driver_probe_device+0x80/0xec
> [    4.266882]  driver_probe_device+0x44/0x150
> [    4.271100]  __driver_attach+0x88/0x1a0
> [    4.274967]  bus_for_each_dev+0x78/0xdc
> [    4.278833]  driver_attach+0x2c/0x40
> [    4.282437]  bus_add_driver+0x15c/0x210
> [    4.286303]  driver_register+0x80/0x13c
> [    4.290170]  __platform_driver_register+0x30/0x3c
> [    4.294915]  of_platform_serial_driver_init+0x24/0x30
> [    4.300013]  do_one_initcall+0x4c/0x240
> [    4.303882]  kernel_init_freeable+0x29c/0x30c
> [    4.308276]  kernel_init+0x2c/0x140
> [    4.311793]  ret_from_fork+0x10/0x20
> [    4.315401] Code: bad PC value
> 
>   drivers/gpio/gpiolib-of.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> index 95be5f0d2623..0e4e1291604d 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -498,6 +498,7 @@ static const of_find_gpio_quirk of_find_gpio_quirks[] = {
>          of_find_regulator_gpio,
>          of_find_arizona_gpio,
>          of_find_usb_gpio,
> +       NULL
>   };
> 
>   struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
> --
> 2.30.2
>