From: Johannes Weiner <hannes@cmpxchg.org>
To: Waiman Long <longman@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Howells <dhowells@redhat.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Joe Perches <joe@perches.com>,
Matthew Wilcox <willy@infradead.org>,
David Rientjes <rientjes@google.com>,
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Subject: Re: [PATCH 1/2] mm, treewide: Rename kzfree() to kfree_sensitive()
Date: Wed, 15 Apr 2020 01:01:06 -0400 [thread overview]
Message-ID: <20200415050106.GA154671@cmpxchg.org> (raw)
In-Reply-To: <20200413211550.8307-2-longman@redhat.com>
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>
next prev parent reply other threads:[~2020-04-15 5:01 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 21:15 [PATCH 0/2] mm, treewide: Rename kzfree() to kfree_sensitive() Waiman Long
2020-04-13 21:15 ` [PATCH 1/2] " Waiman Long
2020-04-14 0:29 ` David Rientjes
2020-04-14 8:32 ` Jason A. Donenfeld
2020-04-14 9:01 ` Michal Hocko
2020-04-14 12:48 ` David Sterba
2020-04-14 18:26 ` Waiman Long
2020-04-15 5:01 ` Johannes Weiner [this message]
2020-06-15 18:07 ` Dan Carpenter
2020-06-15 18:39 ` Waiman Long
2020-04-13 21:15 ` [PATCH 2/2] crypto: Remove unnecessary memzero_explicit() Waiman Long
2020-04-13 21:31 ` Joe Perches
2020-04-13 21:52 ` Waiman Long
2020-04-13 22:28 ` [PATCH v2 " Waiman Long
2020-04-14 6:08 ` Christophe Leroy
2020-04-14 16:24 ` Waiman Long
2020-04-14 19:16 ` Michal Suchánek
2020-04-14 19:37 ` Waiman Long
2020-04-14 19:44 ` Joe Perches
2020-04-14 13:06 ` [PATCH 1/2] mm, treewide: Rename kzfree() to kfree_sensitive() David Howells
2020-04-14 19:29 ` [PATCH v2 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol_info() Waiman Long
2020-04-14 20:02 ` [PATCH v3 2/3] crypto: Remove unnecessary memzero_explicit() Waiman Long
2020-04-16 9:06 ` Corentin Labbe
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