linux-kernel - Re: [PATCH] KERNEL: resource: Fix bug on leakage in /proc/iomem file

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Message-ID: <CAGXu5jLHTzLEsAcF0eHN7xj_Y-jRLtxyjoQVj__AmaXVVSdSzA@mail.gmail.com>
Date:	Wed, 6 Apr 2016 11:21:21 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Emrah Demir <ed@...sec.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	Dave Jones <davej@...hat.com>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KERNEL: resource: Fix bug on leakage in /proc/iomem file

On Wed, Apr 6, 2016 at 11:05 AM,  <ed@...sec.com> wrote:
> First, I wrote your attached patch, but then I thought zeroing other
> /proc/iomem values would be better. So I changed it.
>
> Most distros don't use KASLR, but they use kptr_restrict. Without KASLR,

Well, hopefully that'll change over time. :)

> kptr_restirct most likely useless. As you said these things should be done
> long ago

This results in a warning, but the kernel's printf formatting supports it:

kernel/resource.c: In function ‘r_show’:
kernel/resource.c:118:4: warning: '0' flag used with ‘%p’ gnu_printf
format [-Wformat=]

I'm not sure how to best suppress that...

diff --git a/kernel/resource.c b/kernel/resource.c
index 2e78ead30934..d5881d143fb6 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -111,10 +111,10 @@ static int r_show(struct seq_file *m, void *v)
        for (depth = 0, p = r; depth < MAX_IORES_LEVEL; depth++, p = p->parent)
                if (p->parent == root)
                        break;
-       seq_printf(m, "%*s%0*llx-%0*llx : %s\n",
+       seq_printf(m, "%*s%0*pK-%0*pK : %s\n",
                        depth * 2, "",
-                       width, (unsigned long long) r->start,
-                       width, (unsigned long long) r->end,
+                       width, (void *) r->start,
+                       width, (void *) r->end,
                        r->name ? r->name : "<BAD>");
        return 0;
 }

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security