Messages in this thread | | | Date | Sun, 7 Nov 2010 12:41:56 +0100 | From | Willy Tarreau <> | Subject | Re: [Security] [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking |
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On Sun, Nov 07, 2010 at 12:27:09PM +0100, Ingo Molnar wrote: > > I don't understand the point you're trying to make with this patch. [...] > > It was a simple experiement to support my rather simple argument which you disputed.
OK
> > [...] Obviously we can pretend to be any version, [...] > > Ok, it's a pretty cavalier style of arguing that you now essentially turn around > your earlier claim that the 'kernel version is needed at many places' and say what > i've been saying, prefixed with 'obviously' ;-)
Huh ?
> Yes, it's obvious that the kernel version is not needed for many functional purposes > on a modern distro - and that was my exact point. > > I cannot think of a single valid case where the proper user-space solution to some > ABI compatibility detail is a kernel version check.
Ingo, I believe you did not read a single line of my previous mail, because I precisely gave you counter-examples of that. The first use is simply the user running "uname -a" to see if *he* can safely enable feature X or Y which is known to be badly broken in some old versions.
> I'd even argue that we want to > keep unprivileged user-space from being able to implement such crappy version checks > ...
I'd say that *YOU* want that despite the fact that on mainstream distros, it buys nothing since it's easy to guess the real version anyway as I showed you. Don't forget that you proposed this in order to hide symbols from a small set of well-known distro kernels. And the most important in my opinion is that it does not bring anything to those who are currently victim of exploits : those who don't upgrade, because their uptime alone is enough to *know* that the vuln you want to exploit is still there.
At some places, your proposal would probably end up with uname being chmoded +s so that users stop asking the admin for trivial things. That really makes no sense.
Willy
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