copy_from_user_mmap_sem()

We've all been there; in fact, many of us have been there recently. You wake up to find email from Bugtraq or Full-Disclosure, or perhaps a notification from your vendor about a security update – a security update that affects almost all your systems, and for which exploit code has been publicly available for several days [1]. Of course, I easily could launch into the power of open source and talk about how quickly the Linux kernel team fixed the vulnerability, allowing vendors to push out updates in a timely manner. Or I could talk about the importance of inventorying your systems and having a patch-management system in place so that they can be patched promptly. But the point is this: All systems are vulnerable, all the time. Let me repeat that just to make sure you don't think I made a mistake: All systems are vulnerable, all the time.

Security flaws are a lot like Schrödinger's cat: neither dead nor alive until you look [2] (Figure 1). Do security vulnerabilities appear out of the ether as if by magic when someone observes them, in effect collapsing the quantum probability state of the vulnerability in question to a known state? That is to say, as long as no entity recognizes the security vulnerability (and more importantly, as long as no one has exploit code for it), the vulnerability doesn't really exist. This also is known as the "tree falling in a forest" theory of information security.

Figure 1: The cat is neither dead nor alive, until you look in the box.

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