linux-kernel - Re: [PATCH v2 04/15] x86, kaslr: get kaslr

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Date:	Wed, 4 Mar 2015 13:32:53 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Borislav Petkov <bp@...en8.de>,
	Matt Fleming <matt.fleming@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Jiri Kosina <jkosina@...e.cz>,
	Borislav Petkov <bp@...e.de>, Baoquan He <bhe@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2 04/15] x86, kaslr: get kaslr_enabled back correctly

On Wed, Mar 4, 2015 at 12:00 PM, Ingo Molnar <mingo@...nel.org> wrote:
>
> It is totally unacceptable that you don't do proper analysis of the
> patches you submit, and that you don't bother writing proper, readable
> changelogs.

Sorry, please check it again:

Subject: [PATCH v4] x86, kaslr: Get kaslr_enabled back correctly

commit f47233c2d34f ("x86/mm/ASLR: Propagate base load address calculation")
is using address as value for kaslr_enabled.

That will get wrong value back for kaslr_enabled in kernel stage.
1. When kaslr is not enabled at boot/choose_kernel_location, if kaslr_enabled
get set wrongly in setup.c, late in module.c::get_module_load_offset
will return not wanted random module load offset.
That change behavior when HIBERNATION is defined or nokaslr is passed.

2. When kaslr is enabled at boot/choose_kernel_location, if kaslr_enabled
get cleared wrongly in setup.c, late in module.c::get_module_load_offset
will not return wanted random module load offset.

This patch changes the code to use early_memmap and access the value,
and will keep boot and kernel consistent with kaslr.

-v3: add checking return from early_memmap according to bp.

Fixes: f47233c2d34f ("x86/mm/ASLR: Propagate base load address calculation")
Cc: Matt Fleming <matt.fleming@...el.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Kees Cook <keescook@...omium.org>
Cc: Jiri Kosina <jkosina@...e.cz>
Acked-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
 arch/x86/kernel/setup.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -429,7 +429,18 @@ static void __init reserve_initrd(void)

 static void __init parse_kaslr_setup(u64 pa_data, u32 data_len)
 {
-    kaslr_enabled = (bool)(pa_data + sizeof(struct setup_data));
+    /* kaslr_setup_data is defined in aslr.c */
+    unsigned char *data;
+    unsigned long offset = sizeof(struct setup_data);
+
+    data = early_memremap(pa_data, offset + 1);
+    if (!data) {
+        kaslr_enabled = true;
+        return;
+    }
+
+    kaslr_enabled = *(data + offset);
+    early_memunmap(data, offset + 1);
 }

 static void __init parse_setup_data(void)
--
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