Messages in this thread | | | Date | Sat, 20 Aug 2022 21:51:53 -0700 | From | Dmitry Torokhov <> | Subject | Re: [PATCH] platform/chrome: fix double-free in chromeos_laptop_prepare() |
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On Sat, Aug 20, 2022 at 08:05:13PM +0300, Rustam Subkhankulov wrote: > On Mon, 2022-08-15 at 05:00 +0000, Tzung-Bi Shih wrote: > > Alternatively, I would prefer to fix the double-free by setting > > `i2c_peripherals` to NULL after [1]. > > Since 'cros_laptop->num_i2c_peripherals' is assigned with nonzero value > (otherwise the code on 'err_out' is not executed), setting > 'i2c_peripherals' to NULL after [1] will cause dereferencing of > NULL pointer in chromeos_laptop_destroy() at [2]. > > [1]: > https://elixir.bootlin.com/linux/v5.19/source/drivers/platform/chrome/chromeos_laptop.c#L787 > [2]: > https://elixir.bootlin.com/linux/v5.19/source/drivers/platform/chrome/chromeos_laptop.c#L860 > > > After a quick glance, I found an invalid memory access at [2] if > > `i2c_peripherals` is NULL (see [3]). > > After applying the patch, there will be no invalid memory access at [2] > if 'i2c_peripherals' is NULL, because in this situation > 'cros_laptop->num_i2c_peripherals' is zero and there is no single > iteration of the loop.
Yes, we should either reset both cros_laptop->i2c_peripherals and cros_laptop->num_i2c_peripherals on error, or avoid setting them until we are sure that we are not getting an error. I think prefer the latter.
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Thanks.
-- Dmitry
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