Re: [PATCH] mm/kfence: Null check is added for return value of addr_to_metadata

From: Marco Elver
Date: Fri Sep 24 2021 - 10:14:10 EST

On Fri, 24 Sept 2021 at 15:55, Manjeet Pawar <manjeet.p@xxxxxxxxxxx> wrote:
> This patch add null check for return value of addr_to_metadata().
> currently 'meta' is geting accessed without any NULL check but it is
> usually checked for this function.
> Signed-off-by: Manjeet Pawar <manjeet.p@xxxxxxxxxxx>

Your commit message does not make sense -- what bug did you encounter?

"usually checked for this function" is not a reason to add the check.
Adding a check like this could also hide genuine bugs, as meta should
never be NULL in __kfence_free(). If it is, we'd like to see a crash.

Did you read kfence_free() in include/linux/kfence.h? It already
prevents __kfence_free() being called with a non-KFENCE address.

Without a more thorough explanation, Nack.

-- Marco