Messages in this thread | | | Subject | Re: Out of tree module using LSM | From | Andi Kleen <> | Date | Thu, 29 Nov 2007 22:09:33 +0100 |
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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.)
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