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Date: Wed, 05 Oct 2016 22:52:39 +0200
From: Rasmus Villemoes <linux@...musvillemoes.dk>
To: william.c.roberts@...el.com
Cc: kernel-hardening@...ts.openwall.com, corbet@....net, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: introduce kptr_restrict level 3
On Wed, Oct 05 2016, william.c.roberts@...el.com wrote:
> From: William Roberts <william.c.roberts@...el.com>
>
> Some out-of-tree modules do not use %pK and just use %p, as it's
> the common C paradigm for printing pointers. Because of this,
> kptr_restrict has no affect on the output and thus, no way to
> contain the kernel address leak.
>
> Introduce kptr_restrict level 3 that causes the kernel to
> treat %p as if it was %pK and thus always prints zeros.
>
> Sample Output:
> kptr_restrict == 2:
> p: 00000000604369f4
> pK: 0000000000000000
>
> kptr_restrict == 3:
> p: 0000000000000000
> pK: 0000000000000000
>
> Signed-off-by: William Roberts <william.c.roberts@...el.com>
> ---
> Documentation/sysctl/kernel.txt | 3 ++
> kernel/sysctl.c | 3 +-
> lib/vsprintf.c | 107 ++++++++++++++++++++++++----------------
That's a lot of changed lines. Why isn't this just
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1719,6 +1719,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
case 'G':
return flags_string(buf, end, ptr, fmt);
}
+ if (kptr_restrict == 3)
+ ptr = NULL;
spec.flags |= SMALL;
if (spec.field_width == -1) {
spec.field_width = default_width;
?
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