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Message-ID: <1292649765.10804.42.camel@dan> Date: Sat, 18 Dec 2010 00:22:44 -0500 From: Dan Rosenberg <drosenberg@...curity.com> To: Andrew Morton <akpm@...ux-foundation.org> 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, 2010-12-17 at 17:22 -0800, Andrew Morton wrote: > On Fri, 17 Dec 2010 20:12:39 -0500 > Dan Rosenberg <drosenberg@...curity.com> wrote: > > > > > > > So what's next? We need to convert 1,000,000 %p callsites to use %pK? > > > That'll be fun. Please consider adding a new checkpatch rule which > > > detects %p and asks people whether they should have used %pK. > > > > The goal of this format specifier is specifically for pointers that are > > exposed to unprivileged users. I agree that hiding all kernel pointers > > would be nice, but I don't expect the angry masses to ever agree to > > that. For now, I'll isolate specific cases, especially in /proc, that > > are clear risks in terms of information leakage. I'll also be skipping > > over pointers written to the syslog, since I think hiding that > > information is dmesg_restrict's job. > > Well... some administrators may wish to hide the pointer values even > for privileged callers. That's a pretty trivial add-on for the code > which you have, and means that those admins can also suppress the > pointers for IRQ-time callers. More /proc knobs :) > I can add a "2" setting that hides %pK pointers regardless of privilege level, which I agree is a useful option. But because it would be built into the same format specifier, you still couldn't use %pK in interrupt context (in case the sysctl wasn't set to 2). > Then again, perhaps those admins would be OK if we simply disabled > plain old %p everywhere. In which case we're looking at a separate > patch, I suggest. I would be happy to do this from a security perspective, but I'd imagine there's a pretty high risk of things breaking by doing such a sweeping change. -Dan -- 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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