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Message-Id: <20101217165319.98670d66.akpm@linux-foundation.org> Date: Fri, 17 Dec 2010 16:53:19 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Dan Rosenberg <drosenberg@...curity.com> Cc: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, netdev@...r.kernel.org, jmorris@...ei.org, eugeneteo@...nel.org, kees.cook@...onical.com, mingo@...e.hu, davem@...emloft.net Subject: Re: [PATCH v2] kptr_restrict for hiding kernel pointers from unprivileged users On Fri, 10 Dec 2010 19:05:24 -0500 Dan Rosenberg <drosenberg@...curity.com> wrote: > + case 'K': > + if (kptr_restrict) { > + if (in_irq() || in_serving_softirq() || in_nmi()) > + WARN(1, "%%pK used in interrupt context.\n"); > + > + else if (capable(CAP_SYSLOG)) > + break; > + > + if (spec.field_width == -1) { > + spec.field_width = 2 * sizeof(void *); > + spec.flags |= ZEROPAD; > + } > + return number(buf, end, 0, spec); > + } > + break; Also, we should emit the runtime warning even if kptr_restrict is false. Otherwise programmers might ship buggy code because they didn't enable kptr_restrict during testing. So what I ended up with was case 'K': /* * %pK cannot be used in IRQ context because it tests * CAP_SYSLOG. */ if (in_irq() || in_serving_softirq() || in_nmi()) WARN_ONCE(1, "%%pK used in interrupt context.\n"); if (!kptr_restrict) break; /* %pK does not obscure pointers */ if (capable(CAP_SYSLOG)) break; /* privileged apps expose pointers */ if (spec.field_width == -1) { spec.field_width = 2 * sizeof(void *); spec.flags |= ZEROPAD; } return number(buf, end, 0, spec); How does that look? Also... permitting root to bypass the %pK obscuring seems pretty lame, really. I bet a *lot* of the existing %p sites are already root-only (eg, driver initialisation). So much of the value is lost. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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