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    SubjectRe: Security question: "Text file busy" overwriting executables but not shared libraries?
    Alexander Viro <>:
    > On Tue, 2 Oct 2001, Rob Landley wrote:
    > > Anybody want to venture an opinion why overwriting executable files that are
    > > currently in use gives you a "text file busy" error, but overwriting shared
    > > libraries that are in use apparently works just fine (modulo a core dump if
    > > you aren't subtle about your run-time patching)?
    > >
    > > Permissions are still enforced, but it seems to me somebody who cracks root
    > > on a system could potentially modify the behavior of important system daemons
    > > without changing their process ID numbers.
    > >
    > > Did I miss something somewhere?
    > Somebody who cracks root can attach gdb to a daemon, modify the contents of
    > its text segment and detach. No need to change any files...

    True, but the original problem still appears to be a bug.

    Even the owner of the file should not be able to write to a busy executable,
    whether it is a shared library, or an executable image. Remove it, yes.
    Create a new one (in a different inode) - yes.

    But not modify a busy executable.

    Jesse I Pollard, II

    Any opinions expressed are solely my own.
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