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SubjectRe: [PATCH 1/2] limit print_fatal_signal() rate (was: [RFC] log out-of-virtual-memory events)
On Sat, 19 May 2007 12:33:04 +0200 (MEST) Andrea Righi <righiandr@users.sourceforge.net> wrote:

> Bernd Eckenfels wrote:
> > In article <464DCEAB.3090905@users.sourceforge.net> you wrote:
> >> printk("%s/%d: potentially unexpected fatal signal %d.\n",
> >> current->comm, current->pid, signr);
> >
> > can we have both KERN_WARNING please?
> >
> > Gruss
> > Bernd
>
> Depends on print_fatal_signals patch.
>
> ---
>
> Limit the rate of print_fatal_signal() to avoid potential denial-of-service
> attacks.
>
> 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-vm-log-enomem/kernel/signal.c
> --- linux-2.6.22-rc1-mm1/kernel/signal.c 2007-05-19 11:25:24.000000000 +0200
> +++ linux-2.6.22-rc1-mm1-vm-log-enomem/kernel/signal.c 2007-05-19 11:30:00.000000000 +0200
> @@ -790,7 +790,10 @@ static void print_vmas(void)
>
> static void print_fatal_signal(struct pt_regs *regs, int signr)
> {
> - printk("%s/%d: potentially unexpected fatal signal %d.\n",
> + if (unlikely(!printk_ratelimit()))
> + return;
> +
> + printk(KERN_WARNING "%s/%d: potentially unexpected fatal signal %d.\n",
> current->comm, current->pid, signr);
>
> #ifdef __i386__

Well OK. But vdso-print-fatal-signals.patch is designated not-for-mainline
anyway.

I think the DoS which you identify has been available for a very long time
on ia64, x86_64 and perhaps others.


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