Re: [Cocci] [PATCH 1/2] mm, treewide: Rename kzfree() to kfree_sensitive()

[Johannes Weiner <hannes@cmpxchg.org>]

On Mon, Apr 13, 2020 at 05:15:49PM -0400, Waiman Long wrote:
> As said by Linus:
> 
>   A symmetric naming is only helpful if it implies symmetries in use.
>   Otherwise it's actively misleading.

As the btrfs example proves - people can be tempted by this false
symmetry to pair kzalloc with kzfree, which isn't what we wanted.

>   In "kzalloc()", the z is meaningful and an important part of what the
>   caller wants.
> 
>   In "kzfree()", the z is actively detrimental, because maybe in the
>   future we really _might_ want to use that "memfill(0xdeadbeef)" or
>   something. The "zero" part of the interface isn't even _relevant_.
> 
> The main reason that kzfree() exists is to clear sensitive information
> that should not be leaked to other future users of the same memory
> objects.
> 
> Rename kzfree() to kfree_sensitive() to follow the example of the
> recently added kvfree_sensitive() and make the intention of the API
> more explicit. In addition, memzero_explicit() is used to clear the
> memory to make sure that it won't get optimized away by the compiler.
> 
> The renaming is done by using the command sequence:
> 
>   git grep -w --name-only kzfree |\
>   xargs sed -i 's/\bkzfree\b/kfree_sensitive/'
> 
> followed by some editing of the kfree_sensitive() kerneldoc and the
> use of memzero_explicit() instead of memset().
> 
> Suggested-by: Joe Perches <joe@perches.com>
> Signed-off-by: Waiman Long <longman@redhat.com>

Looks good to me. Thanks for fixing this very old mistake.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>
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