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    SubjectRe: Linux inode.i_count overflow
    Hi!

    > > Member i_count in struct inode contains the usage count. It is of type
    > > unsigned short, which is only 16-bit long on i386. Unfortunately, it
    > > is not enough. You can make it overflow by mapping one file many
    > > times:
    >
    > Making i_count unsigned long fixes this (Im sure its simple enough not to
    > need a patch). This should be in 2.0.34

    Ok, it is simple, but *PLEASE* post that patch anyway.

    Also, I do not like that solution. Expands structure a bit. Is it
    possible to do overflow detection (if (i_count > 32000) return
    EOPIMPOSSIBLEBECAUSEIDONTLIKEYOU?)? Even kill process with -9 would be
    enough, I believe.

    Also, how resistant is 2.1.79 to this kind of attack?

    > This seems to be a generic Unix bug. I brought down our SGI with that
    > program, and netbsd also seems to jam solid. The general vulnerability
    > is going to be the same on all OS's (anyone got an NT port ?) or want
    > to make a summary table.

    Ok, but I believe that even generic linux bugs should be solved. Well,
    my solution would be to go for mixie ;-). I believe that this is hard
    to do. Actually, it may be impossible before Jakub Jelinek finishes his
    work on dealocating page tables early.

    Pavel
    --
    I'm really pavel@atrey.karlin.mff.cuni.cz. Pavel
    Look at http://atrey.karlin.mff.cuni.cz/~pavel/ ;-).

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