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    SubjectRe: [RFC] [-mm] Remove 'unsafe' LZO decompressor
    Date
    On 24 May 2007, at 19:50, Andrew Morton wrote:

    > On Thu, 24 May 2007 18:15:17 +0100
    > Michael-Luke Jones <mlj28@cam.ac.uk> wrote:
    >
    >> 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 :)
    >
    > This is obviously a highly desirable thing to do for a number of
    > reasons.
    > But have we quantified the performance difference?

    The author of LZO may be able to help us out here, so he's CCed as of
    this mail.

    Michael-Luke

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