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    SubjectRe: Out of tree module using LSM
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    Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

    > If I want I can have 16 threads executing code in a shared object being
    > written to by ten other programs at once and shared over a network while
    > we are at it. Its probably not a good idea but I can do it if I have
    > reason to.

    Actually the kernel prevents writing to files which are executed currently
    and you can also not execute what is currently open for writing.
    That is what VM_DENYWRITE is good for.

    Does not work for shared libraries though -- you cannot set VM_DENYWRITE
    in user mmap aka ld.so Man page says

    MAP_DENYWRITE
    This flag is ignored. (Long ago, it signalled that attempts to write to the underlying file should fail
    with ETXTBUSY. But this was a source of denial-of-service attacks.)

    -Andi
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