linux-kernel - Re: [PATCH] kdbus: fix type conversion in item macroses

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Message-ID: <CANq1E4TkyBiJQuZG5Qt810176Be6==RxD4AWsw41TbKZ7d8dLw@mail.gmail.com>
Date:	Thu, 4 Jun 2015 13:26:03 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	Sergei Zviagintsev <sergei@...v.net>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Djalal Harouni <tixxdz@...ndz.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kdbus: fix type conversion in item macroses

Hi

On Thu, Jun 4, 2015 at 12:39 PM, Sergei Zviagintsev <sergei@...v.net> wrote:
> KDBUS_ITEM_NEXT and KDBUS_ITEMS_END macroses do not enclose _i argument
> into parentheses when applying the cast operator. If complex expression
> passed, e.g.
>
>     KDBUS_ITEM_NEXT(condition ? a : b)
>
> then type conversion to (u8 *) will go wrong due to precedence rules.
>
> Use parentheses properly. Update documentation.
>
> Signed-off-by: Sergei Zviagintsev <sergei@...v.net>
> ---
>  Documentation/kdbus/kdbus.item.xml | 2 +-
>  ipc/kdbus/item.h                   | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)

Reviewed-by: David Herrmann <dh.herrmann@...il.com>

Thanks
David

> diff --git a/Documentation/kdbus/kdbus.item.xml b/Documentation/kdbus/kdbus.item.xml
> index 09f8b903116f..b0eeeef995af 100644
> --- a/Documentation/kdbus/kdbus.item.xml
> +++ b/Documentation/kdbus/kdbus.item.xml
> @@ -69,7 +69,7 @@
>  #define KDBUS_ALIGN8(val) (((val) + 7) & ~7)
>
>  #define KDBUS_ITEM_NEXT(item) \
> -    (typeof(item))(((uint8_t *)item) + KDBUS_ALIGN8((item)->size))
> +    (typeof(item))((uint8_t *)(item) + KDBUS_ALIGN8((item)->size))
>
>  #define KDBUS_ITEM_FOREACH(item, head, first)                      \
>      for (item = (head)->first;                                     \
> diff --git a/ipc/kdbus/item.h b/ipc/kdbus/item.h
> index eeefd8beac3b..03612368b3bb 100644
> --- a/ipc/kdbus/item.h
> +++ b/ipc/kdbus/item.h
> @@ -21,7 +21,7 @@
>  #include "util.h"
>
>  /* generic access and iterators over a stream of items */
> -#define KDBUS_ITEM_NEXT(_i) (typeof(_i))(((u8 *)_i) + KDBUS_ALIGN8((_i)->size))
> +#define KDBUS_ITEM_NEXT(_i) (typeof(_i))((u8 *)(_i) + KDBUS_ALIGN8((_i)->size))
>  #define KDBUS_ITEMS_SIZE(_h, _is) ((_h)->size - offsetof(typeof(*_h), _is))
>  #define KDBUS_ITEM_HEADER_SIZE offsetof(struct kdbus_item, data)
>  #define KDBUS_ITEM_SIZE(_s) KDBUS_ALIGN8(KDBUS_ITEM_HEADER_SIZE + (_s))
> @@ -40,7 +40,7 @@
>          (u8 *)(_i) >= (u8 *)(_is))
>
>  #define KDBUS_ITEMS_END(_i, _is, _s)                                   \
> -       ((u8 *)_i == ((u8 *)(_is) + KDBUS_ALIGN8(_s)))
> +       ((u8 *)(_i) == ((u8 *)(_is) + KDBUS_ALIGN8(_s)))
>
>  /**
>   * struct kdbus_item_header - Describes the fix part of an item
> --
> 1.8.3.1
>
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