linux-kernel - Re: sendmmsg: put_user vs __put

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Message-Id: <20120331.172710.540592519617177028.davem@davemloft.net>
Date:	Sat, 31 Mar 2012 17:27:10 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	drepper@...il.com
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: sendmmsg: put_user vs __put_user

From: Ulrich Drepper <drepper@...il.com>
Date: Sat, 31 Mar 2012 08:30:25 -0400

> On Fri, Mar 30, 2012 at 20:51, David Miller <davem@...emloft.net> wrote:
>> Compat processes are not able to generate virtual addresses anywhere
>> near the range where the kernel resides, so the address range
>> verification done by put_user() is completely superfluous and
>> therefore not necessary.  The normal exception handling done by the
>> access is completely sufficient.
> 
> I was more thinking about the effects of might_fault() then additional tests.

This is very clearly in a context where locks are not held and sleeping
would be fine, so I don't see any value in that either.
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