On Mon, 04 Feb 2002 20:09:20 PST, Chris Wright said: > ah, i see, good question. i can't think of any from the top of my > head. not all hooks are in a syscall path, some will be called from an > interrupt context, e.g. ip layer hooks, or send_sigiotask. but it's not > necessarily a recipe for async notification to user app. it is possible Yes, but if it *is* a recipe for async notification, we need to have a handle on how/what happens... > that a security policy violation could result in sending the app SIGKILL. How rude. ;) Actually, having a *documented* "you can SEGV if your mmap() is revoked" would be tolerable. It's the fun&games of trying to *debug* an application crash that's getting a "cant happen" SEGV (and of trying to write a signal handler that will Do The Right Thing). > it's also possible that an app is waiting for SIGIO, but it never arrives. > but neither of these really fall into the category you're asking about. > food for thought ;-) Exactly - Linux has never been incredibly strong at asynchronous event handling (I'm meaning "strong" the way IBM's mainframe systems are "strong" at it - WAIT/POST and async I/O were a solved problem in the early 60s and they've gotten better at it since). One headache is that the Linux signal mechanism seems to be stuck with 32 non-realtime signals, and they're all taken, so there isn't even the option of defining a new SIGREVOKE or something, and doing things that way. As a counter-example, AIX allows a lot more signals, so they can afford stuff like SIGDANGER to a process so it can try to free up memory (a lot nicer than the "kill -9 a likely process" route if you run out of swap), or a SIGXCPU if you've exceeded a CPU usage limit, etc etc. They've even got this gem: #define SIGPRE 36 /* programming exception */ (There's also a 'SIGSAK' telling you the Secure Attention Key has been hit, but that's neither here nor there - or is it? ;) How much properly-written code would break if the value of _NSIG in bits/signum.h chagned from 64 to 96 or 128? ;) (Yes, I know the Powers That Be would probably have a *cow* at the idea, but the 2.5 kernel would be the time to get ourselves a SIGREVOKE and SIGSAK, wouldn't it? ;) /Valdis _______________________________________________ linux-security-module mailing list linux-security-moduleat_private http://mail.wirex.com/mailman/listinfo/linux-security-module
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