linux-kernel - Re: [PATCH] rbtree: use designated initializers

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Message-ID: <20161217135820.GA3107@twins.programming.kicks-ass.net>
Date:   Sat, 17 Dec 2016 14:58:20 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jie Chen <fykcee1@...il.com>
Subject: Re: [PATCH] rbtree: use designated initializers

On Fri, Dec 16, 2016 at 05:02:53PM -0800, Kees Cook wrote:
> Prepare to mark sensitive kernel structures for randomization by making
> sure they're using designated initializers. These were identified during
> allyesconfig builds of x86, arm, and arm64, with most initializer fixes
> extracted from grsecurity.

Works for me.

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

One note on these structures, the intent is that GCC value propagation
completely does away with everything and results in inlining the actual
functions. Older versions of GCC had a wee bit of trouble with this, but
recent versions do just that, not a single actual structure should end
up being emitted in the object code.

> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  include/linux/rbtree_augmented.h | 4 +++-
>  lib/rbtree.c                     | 4 +++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/rbtree_augmented.h b/include/linux/rbtree_augmented.h
> index d076183e49be..9702b6e183bc 100644
> --- a/include/linux/rbtree_augmented.h
> +++ b/include/linux/rbtree_augmented.h
> @@ -90,7 +90,9 @@ rbname ## _rotate(struct rb_node *rb_old, struct rb_node *rb_new)	\
>  	old->rbaugmented = rbcompute(old);				\
>  }									\
>  rbstatic const struct rb_augment_callbacks rbname = {			\
> -	rbname ## _propagate, rbname ## _copy, rbname ## _rotate	\
> +	.propagate = rbname ## _propagate,				\
> +	.copy = rbname ## _copy,					\
> +	.rotate = rbname ## _rotate					\
>  };
>  
>  
> diff --git a/lib/rbtree.c b/lib/rbtree.c
> index 1f8b112a7c35..4ba2828a67c0 100644
> --- a/lib/rbtree.c
> +++ b/lib/rbtree.c
> @@ -427,7 +427,9 @@ static inline void dummy_copy(struct rb_node *old, struct rb_node *new) {}
>  static inline void dummy_rotate(struct rb_node *old, struct rb_node *new) {}
>  
>  static const struct rb_augment_callbacks dummy_callbacks = {
> -	dummy_propagate, dummy_copy, dummy_rotate
> +	.propagate = dummy_propagate,
> +	.copy = dummy_copy,
> +	.rotate = dummy_rotate
>  };
>  
>  void rb_insert_color(struct rb_node *node, struct rb_root *root)
> -- 
> 2.7.4
> 
> 
> -- 
> Kees Cook
> Nexus Security