linux-kernel - Re: [PATCH 3/3] ipc: compat: use signed size

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Date:	Wed, 11 Jul 2012 12:06:55 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Will Deacon <will.deacon@....com>
CC:	<linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
	<davem@...emloft.net>, <chris@...kel.net>,
	<catalin.marinas@....com>, <arnd@...db.de>,
	<akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/3] ipc: compat: use signed size_t types for msgsnd and
 msgrcv

On 7/11/2012 11:32 AM, Will Deacon wrote:
> The msgsnd and msgrcv system calls use size_t to represent the size of
> the message being transferred. POSIX states that values of msgsz greater
> than SSIZE_MAX cause the result to be implementation-defined. On Linux,
> this equates to returning -EINVAL if (long) msgsz < 0.
>
> For compat tasks where !CONFIG_ARCH_WANT_OLD_COMPAT_IPC and
> compat_size_t is smaller than size_t, negative size values passed from
> userspace will be interpreted as positive values by do_msg{rcv,snd} and
> will fail to exit early with -EINVAL.
>
> This patch changes the compat prototypes for msg{rcv,snd} so that the
> message size is represented as a compat_ssize_t, which we cast to the
> native ssize_t type for the core IPC code.
>
> Cc: Arnd Bergmann <arnd@...db.de>
> Acked-by: Catalin Marinas <catalin.marinas@....com>
> Signed-off-by: Will Deacon <will.deacon@....com>
> ---
>  include/linux/compat.h |    4 ++--
>  ipc/compat.c           |    8 ++++----
>  2 files changed, 6 insertions(+), 6 deletions(-)

Acked-by: Chris Metcalf <cmetcalf@...era.com>

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com



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