Subject: __user and iov_base
From: Steve French <smfltc@us.ibm.com>
To: linux-kernel@vger.kernel.org
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Organization: IBM
Message-Id: <1087235597.10368.12.camel@stevef95.austin.ibm.com>
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Date: 14 Jun 2004 12:53:18 -0500
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Sender: linux-kernel-owner@vger.kernel.org
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The commonly used kernel structure iovec includes a field iov_base which
is:
	void __user *iov_base

Unfortunately some of the places that use this are sockets calls from
kernel code in which it would be awkward to do extra memcpy to a user
buffer (from a kernel buffer, perhaps created in a different process)
just to avoid a sparse warning.   Although it works fine to set
	myiovec.iov_base = (char *)some_buffer; 
this generates a warning message in the sparse tool since iov_base
includes the __user modifier, and the kernel buffer you are sending does
not..

If a buffer is never used in user space, and is potentially recycled
(via mempools) for use by more than one process, then it can't be passed
around as an __user buffer, but is it ok to simply do
	myiovec.iov_base = (__user char *)some_buffer; 
or is there another preferred way to handle kernel to __user
mappings/casts?

For the cifs vfs this would eliminate the last sparse warnings. 
	

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