Crash

[manu_9]

Can a Unix system crash by a non root user process.If yes , why does and under which circumstance it happens .

[Mark Grant]

No problem at all if permissions on things are not set correctly.

I imagine if you have user write permission on /dev/kmem for example and you write a load of random muck to it, the system would crash.

Or simply, haveing user write permission on / and doing an rm -r probably wouldn't do the system much good either.

Generally speaking though it isn't too easy for a non-root user to crash the system

[manu_9]

But if permissions on the kernel dir are correct.What can be the causes of crash .Like if user runs a process , it can become a kernel thread and can cause crash ....thoughts ????

[Cheryl Griffin]

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[Mark Grant]

One of the reasons that unix is such a good thing is that it has always been impossible for a user process to corrupt system memory etc. I would hate to hear that a user can create a kernel thread that can interact with kernel data structures. That way lies death (or Windows).

However, there are other things a user can do. You can persuade some root owned process to crash the system or at least render it useless. For example any user can flood an http port with lengthy requests to bring a server to its knees if the system doesn't protect against it.

Maybe you have some software that is installed that runs as root and it loads a data file and does some work with it. Any user with access to the software could perhaps add incorrect data to the datafile, perhaps by mistake, and if the software isn't written too well the result might be a crash or an inoperable system.

The point is, that kernel crashes themselves are very rare but there are a million other ways to bring a system down.