Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel

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Xiaotian Feng a Ãcrit :
On Thu, Dec 23, 2010 at 5:35 AM,  <Valdis.Kletnieks@xxxxxx> wrote:
On Wed, 22 Dec 2010 13:40:19 +0100, Ingo Molnar said:
* mat <castet.matthieu@xxxxxxx> wrote:

Le Wed, 8 Dec 2010 14:19:51 -0800,
Kees Cook <kees.cook@xxxxxxxxxxxxx> a Ãcrit :

On Fri, Nov 26, 2010 at 06:23:55PM +0100, mat wrote:
could you try the attached patch ?

on module load, we sort the __jump_table section. So we should make
it writable.


Matthieu
diff --git a/arch/x86/include/asm/jump_label.h
b/arch/x86/include/asm/jump_label.h index f52d42e..574dbc2 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -14,7 +14,7 @@
        do
{                                                       \ asm
goto("1:"                                       \
JUMP_LABEL_INITIAL_NOP                  \
-                       ".pushsection __jump_table,  \"a\" \n\t"\
+                       ".pushsection __jump_table,  \"aw\" \n\t"\
                        _ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
                        ".popsection \n\t"                      \
                        : :  "i" (key) :  : label);
\
Acked-by: Kees Cook <kees.cook@xxxxxxxxxxxxx>

Can this please get committed to tip?
I think it is not need anymore with  Steven Rostedt patch [1]

Matthieu

[1]
Here we set the text read only before we call the notifiers. The
function tracer changes the calls to mcount into nops via a notifier
call so this must be done after the module notifiers.
What's the status of this bug?

If we still need the patch then please submit it standalone with a proper subject
line, with acks/signoffs added, etc.
Steve Rostedt's patch that moves the setting of the page permissions seems to
make this patch no longer necessary.  I tripped over this same issue, but the
version in the latest -mmotm does not need it, as it includes Steve's fix.


I'm facing a boot failure (panic'ed on remove_jump_label_module_init)
on 2.6.37 (latest commit 3c0cb7c), which is 100% reproducible.
With this patch applied, I can boot my machine successfully, so I do
think this patch is needed.

Could you confirm that this patch fix the problem ?


Matthieu
>From 0eeba453aaba0ebff86f0a7ad9bfb8afbde0c0dc Mon Sep 17 00:00:00 2001
From: Matthieu CASTET <castet.matthieu@xxxxxxx>
Date: Thu, 20 Jan 2011 21:25:03 +0100
Subject: [PATCH] Fix jump table in module init section

If we use jump table in module init, there are marked
as removed in __jump_table section after init is done.

But we already applied ro permissions on the module, so
we can't modify a read only section (crash in
remove_jump_label_module_init).

Make the __jump_table section rw.

Signed-off-by: Matthieu CASTET <castet.matthieu@xxxxxxx>
---
 arch/x86/include/asm/jump_label.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index f52d42e..574dbc2 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -14,7 +14,7 @@
 	do {							\
 		asm goto("1:"					\
 			JUMP_LABEL_INITIAL_NOP			\
-			".pushsection __jump_table,  \"a\" \n\t"\
+			".pushsection __jump_table,  \"aw\" \n\t"\
 			_ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
 			".popsection \n\t"			\
 			: :  "i" (key) :  : label);		\
-- 
1.7.2.3


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