From: "H. Peter Anvin" <hpa@zytor•com>
To: Florian Westphal <fw@strlen•de>
Cc: linux-fsdevel@vger•kernel.org, Al Viro <viro@zeniv•linux.org.uk>,
"David S. Miller" <davem@davemloft•net>,
Thomas Gleixner <tglx@linutronix•de>, Ingo Molnar <mingo@elte•hu>,
x86@kernel•org, netdev@vger•kernel.org,
linux-kernel@vger•kernel.org
Subject: Re: [PATCH -next] x86, fs: add sys_compat_write for net/socket.c
Date: Tue, 30 Mar 2010 10:56:05 -0700 [thread overview]
Message-ID: <4BB23B35.7060401@zytor.com> (raw)
In-Reply-To: <1269971469-1254-1-git-send-email-fw@strlen.de>
On 03/30/2010 10:51 AM, Florian Westphal wrote:
> On some configurations, e.g. x86_64 with 32bit userspace, netlink/xfrm
> misinterprets messages from userspace due to different structure
> layout (u64 has different alignment requirements on x86 vs. x86_64).
>
> As long as messages are sent via sendmsg(), this could be handled via
> net/compat.c; it will set the CMSG_MSG_COMPAT flag in struct msghdr
> for compat tasks, which would allow to the xfrm_user code to detect
> when messages need compat fixups.
>
> Unfortunately, some programs (e.g. pluto ike daemon), send netlink data
> to the kernel using write().
>
> Thus, introduce f_ops->compat_aio_write and compat_sys_write to treat
> writes on sockets specially.
>
> This only wires up compat_sys_write for x86/x86_64 -- at the moment this
> is only required to parse xfrm netlink messages, which happen to only
> need special treatment in case of COMPAT_FOR_U64_ALIGNMENT=y.
>
> Setting CMSG_MSG_COMPAT depending on plain is_compat_task() in net/socket.c
> was not done due to concerns regarding the kernel doing socket
> writes in response to a user event (which might set MSG_COMPAT erronously).
>
OK... I have to ask the question:
This only applies if you're using unpacked structures with
non-naturally-aligned objects in them. Where to we have those, and can
we shoot the authors?
-hpa
next parent reply other threads:[~2010-03-30 17:56 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1269971469-1254-1-git-send-email-fw@strlen.de>
2010-03-30 17:56 ` H. Peter Anvin [this message]
2010-03-30 18:17 ` [PATCH -next] x86, fs: add sys_compat_write for net/socket.c Florian Westphal
2010-03-30 18:48 ` Arnd Bergmann
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