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Date: Wed, 6 Apr 2016 11:21:21 -0700
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Subject: Re: [PATCH] KERNEL: resource: Fix bug on leakage in /proc/iomem file
From: Kees Cook <keescook@chromium.org>
To: Emrah Demir <ed@abdsec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Dan Rosenberg <dan.j.rosenberg@gmail.com>,
        Dave Jones <davej@redhat.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Apr 6, 2016 at 11:05 AM,  <ed@abdsec.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