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    SubjectRe: PATCH: signals security
    On Wed, 20 May 1998, Pavel Machek wrote:

    > > > + * 1998-05-19 Security fix: don't allow SIGKILL & friends just because
    > > > + * you have same real uid. Pavel Machek
    > >
    > > Catastrophe. I can no longer kill processes I created that happened to be
    > > setuid. Please _THINK_ what you are trying to achieve, and understand why
    >
    > Ok - what I'm trying to achieve is that user will no longer be able to
    > kill suid X server with SIGKILL. Please take a look at code: you still

    Let me summarize:
    - you want to disallow SIGKILL to processes which do raw I/O
    - so you check for the suid() bit.

    This is obviously _not_ correct, since:
    - raw I/O will be a capability CAP_RAW_IO
    - root may have some raw-I/O programs that are _not_ suid,
    since root is the only one who is allowed to use the program

    You are probably better off using some of the code in
    my Out-Of-Memory killer. It checks:
    - whether the x86 I/O bitmap has been set up
    - whether the process has raw I/O capability (CAP_RAW_IO)

    Now we probably want to modify the ioperm() and iopl()
    syscalls to set CAP_RAW_IO, so we can do an easy arch
    independant check.
    (the capability itself is in the allowed bitmap and
    it should only be set in the current bitmap when it's
    actually used)

    Rik.
    +-------------------------------------------+--------------------------+
    | Linux: - LinuxHQ MM-patches page | Scouting webmaster |
    | - kswapd ask-him & complain-to guy | Vries cubscout leader |
    | http://www.phys.uu.nl/~riel/ | <H.H.vanRiel@phys.uu.nl> |
    +-------------------------------------------+--------------------------+


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