linux-kernel - [RFC] [-mm] Remove 'unsafe' LZO decompressor

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Message-Id: <1412F214-FA89-4088-B3A2-DEE03C324FB6@cam.ac.uk>
Date:	Thu, 24 May 2007 18:15:17 +0100
From:	Michael-Luke Jones <mlj28@....ac.uk>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Richard Purdie <richard@...nedhand.com>
Subject: [RFC] [-mm] Remove 'unsafe' LZO decompressor

Hi there,

Attached is a patch which may be desirable for -mm. It applies  
directly to 2.6.22-rc2-mm1.

The patch removes the 'unsafe' LZO decompression function, lowering  
the size of the minilzo.c file by nearly 500 out of an original 1727  
lines. It also removes references to the 'unsafe' decompression  
function in the public LZO header and the EXPORT_SYMBOL_GPL declaration.

This is intended to provoke some discussion over whether a  
decompression function able to scribble on arbitrary memory is  
desirable in the mainline kernel, whatever the performance increases.

Over and above the security/stability implications of using this  
code, it can also be argued to represent an unnecessary duplication  
of the vast majority of LZO decompression code. This is due to the  
lack of likely in-kernel uses of the 'unsafe' function.

Only a single user for this 'unsafe' code has been suggested, the  
'Compressed Caching' project. This code is highly unlikely to move  
into mainline in the same timeframe as the LZO code. All of the other  
suggested uses require decompression of untrusted data, such that the  
'safe' function should be used.

Comments / disagreement all welcome :)

Michael-Luke Jones

Download attachment "lzo-remove-unsafe-decompressor.patch" of type "application/octet-stream" (15243 bytes)