Re: [PATCH] drm: mali-dp: Add check for kzalloc
From: Jiasheng Jiang
Date: Wed Dec 07 2022 - 21:15:59 EST
On Wed, Dec 07, 2022 at 09:59:04PM +0800, Robin Murphy wrote:
>> As kzalloc may fail and return NULL pointer, it should be better to check
>> the return value in order to avoid the NULL pointer dereference in
>> __drm_atomic_helper_connector_reset.
>
> This commit message is nonsense; if
> __drm_atomic_helper_connector_reset() would dereference the NULL implied
> by &mw_state->base, it would equally still dereference the explicit NULL
> pointer passed after this patch.
>
> The current code works out OK because "base" is the first member of
> struct malidp_mw_connector_state, thus if mw_state is NULL then
> &mw_state->base == NULL + 0 == NULL. Now you *could* argue that this
> isn't robust if the layout of struct malidp_mw_connector_state ever
> changes, and that could be a valid justification for making this change,
> but the reason given certainly isn't.
>
> Arithmetic on a (potentially) NULL pointer may well be a sign that it's
> worth a closer look to check whether it really is what the code intended
> to do, but don't automatically assume it has to be a bug. Otherwise,
> good luck with "fixing" every user of container_of() throughout the
> entire kernel.
I have sent a new patch with the modified commit mesage.
Thanks,
Jiang