Messages in this thread Patch in this message | | | From | Andrea Righi <> | Subject | Re: [RFC] log out-of-virtual-memory events | Date | Fri, 18 May 2007 18:05:11 +0200 (MEST) |
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Andrea Righi wrote: > Robin Holt wrote: >> On Fri, May 18, 2007 at 09:50:03AM +0200, Andrea Righi wrote: >>> Rik van Riel wrote: >>>> Andrea Righi wrote: >>>>> I'm looking for a way to keep track of the processes that fail to >>>>> allocate new >>>>> virtual memory. What do you think about the following approach >>>>> (untested)? >>>> Looks like an easy way for users to spam syslogd over and >>>> over and over again. >>>> >>>> At the very least, shouldn't this be dependant on print_fatal_signals? >>>> >>> Anyway, with print-fatal-signals enabled a user could spam syslogd too, simply >>> with a (char *)0 = 0 program, but we could always identify the spam attempts >>> logging the process uid... >>> >>> In any case, I agree, it should depend on that patch... >>> >>> What about adding a simple msleep_interruptible(SOME_MSECS) at the end of >>> log_vm_enomem() or, at least, a might_sleep() to limit the potential spam/second >>> rate? >> An msleep will slow down this process, but do nothing about slowing >> down the amount of logging. Simply fork a few more processes and all >> you are doing with msleep is polluting the pid space. >> > > Very true. > >> What about a throttling similar to what ia64 does for floating point >> assist faults (handle_fpu_swa()). There is a thread flag to not log >> the events at all. It is rate throttled globally, but uses per cpu >> variables for early exits. This algorithm scaled well to a thousand >> cpus. > > Actually using printk_ratelimit() should be enough... BTW print_fatal_signals() > should use it too. >
I mean, something like this...
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Limit the rate of the printk()s in print_fatal_signal() to avoid potential DoS problems.
Signed-off-by: Andrea Righi <a.righi@cineca.it>
diff -urpN linux-2.6.22-rc1-mm1/kernel/signal.c linux-2.6.22-rc1-mm1-limit-print_fatal_signals-rate/kernel/signal.c --- linux-2.6.22-rc1-mm1/kernel/signal.c 2007-05-18 17:48:55.000000000 +0200 +++ linux-2.6.22-rc1-mm1-limit-print_fatal_signals-rate/kernel/signal.c 2007-05-18 17:58:13.000000000 +0200 @@ -790,6 +790,9 @@ static void print_vmas(void) static void print_fatal_signal(struct pt_regs *regs, int signr) { + if (unlikely(!printk_ratelimit())) + return; + printk("%s/%d: potentially unexpected fatal signal %d.\n", current->comm, current->pid, signr); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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