Messages in this thread | | | Subject | Re: [PATCH v3] vsprintf: Check real user/group id for %pK | From | Joe Perches <> | Date | Wed, 09 Oct 2013 15:33:50 -0700 |
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On Thu, 2013-10-10 at 09:25 +1100, Ryan Mallon wrote:
> if (kptr_restrict && (in_irq() || in_serving_softirq() || > in_nmi())) { > > Is making sure that you don't have kernel code doing something like this: > > irqreturn_t some_irq_handler(int irq, void *data) > { > struct seq_file *seq = to_seq(data); > > seq_printf(seq, "value = %pK\n"); > return IRQ_HANDLED; > } > > Because that obviously won't work when kptr_restrict=1 (because the > CAP_SYSLOG check is meaningless). However, the code is broken regardless > of the kptr_restrict value.
The only brokenness I see here is that the code doesn't pass a pointer along with %pK
seq_printf(seq, "value of seq: %pK\n", seq);
> Since the default value of kptr_restrict is > 0, this kind of bug can go over-looked because the seq file will print > the pointer value correctly when kptr_restrict=0, and it will correctly > print 0's when kptr_restrict=2, but it will print 'pK-error' when > kptr_restrict=1. Doing the check in all cases makes it more likely that > bugs like this get found. In fact, doing something like: > > if (WARN_ON(in_irq() || in_serving_softirq() || in_nmi())) { > > Might be better, since that will print a stack-trace showing where the > offending vsprintf is.
WARN_ON would be potentially _very_ noisy. Maybe a long period (once a day?) ratelimited dump_stack();
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