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

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Date:	Wed, 24 Nov 2010 22:41:07 -0500
From:	Valdis.Kletnieks@...edu
To:	matthieu castet <castet.matthieu@...e.fr>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-next@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Dave Jones <davej@...hat.com>,
	Siarhei Liakh <sliakh.lkml@...il.com>,
	Kees Cook <kees.cook@...onical.com>
Subject: Re: [PATCH 3/3 V13] RO/NX protection for loadable kernel

On Tue, 16 Nov 2010 22:35:16 +0100, matthieu castet said:

> This patch is a logical extension of the protection provided by
> CONFIG_DEBUG_RODATA to LKMs. The protection is provided by splitting
> module_core and module_init into three logical parts each and setting
> appropriate page access permissions for each individual section:
> 
>  1. Code: RO+X
>  2. RO data: RO+NX
>  3. RW data: RW+NX

This is incompatible with CONFIG_JUMP_LABEL:

[  252.093624] BUG: unable to handle kernel paging request at ffffffffa0680764
[  252.094008] IP: [<ffffffff81225ee0>] generic_swap+0xa/0x1a
[  252.094008] PGD 1a1e067 PUD 1a22063 PMD 1093ac067 PTE 8000000109786161
[  252.094008] Oops: 0003 [#1] PREEMPT SMP 

[  252.094008] Pid: 3740, comm: modprobe Not tainted 2.6.37-rc3-mmotm1123 #1 0X564R/Latitude E6500                  
[  252.094008] RIP: 0010:[<ffffffff81225ee0>]  [<ffffffff81225ee0>] generic_swap+0xa/0x1a
[  252.094008] RSP: 0018:ffff88011a217d98  EFLAGS: 00010206
[  252.094008] RAX: 00000000000000d9 RBX: 0000000000000030 RCX: 000000000000007c
[  252.094008] RDX: 0000000000000017 RSI: ffffffffa0680794 RDI: ffffffffa0680764
[  252.094008] RBP: ffff88011a217d98 R08: 0000000000000000 R09: ffff88011a217d38
[  252.094008] R10: 0000000000000000 R11: 000000000000013d R12: ffffffffa0680764
[  252.094008] R13: 0000000000000018 R14: 0000000000000018 R15: 0000000000000018
[  252.094008] FS:  00007f6ecb897720(0000) GS:ffff8800df100000(0000) knlGS:0000000000000000
[  252.094008] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[  252.094008] CR2: ffffffffa0680764 CR3: 000000011911e000 CR4: 00000000000406e0
[  252.094008] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  252.094008] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[  252.094008] Process modprobe (pid: 3740, threadinfo ffff88011a216000, task ffff88011861e300)
[  252.094008] Stack:
[  252.094008]  ffff88011a217e28 ffffffff81226007 ffffffff81a31158 0000000000000000
[  252.094008]  0000000000000030 0000000000000048 ffffffff8105fa34 ffffffff81225ed6
[  252.094008]  ffffffff00000018 ffffffff00000018 0000000000000018 00000030ffffffff
[  252.094008] Call Trace:
[  252.094008]  [<ffffffff81226007>] sort+0x117/0x1b0
[  252.094008]  [<ffffffff8105fa34>] ? jump_label_cmp+0x0/0x1b
[  252.094008]  [<ffffffff81225ed6>] ? generic_swap+0x0/0x1a
[  252.094008]  [<ffffffff8105faa6>] sort_jump_label_entries+0x2b/0x2d
[  252.094008]  [<ffffffff8105feda>] jump_label_module_notify+0x58/0x253
[  252.094008]  [<ffffffff8155e816>] notifier_call_chain+0x54/0x81
[  252.094008]  [<ffffffff8105d9b2>] __blocking_notifier_call_chain+0x5c/0x79
[  252.094008]  [<ffffffff8105d9de>] blocking_notifier_call_chain+0xf/0x11
[  252.094008]  [<ffffffff810778cc>] sys_init_module+0x76/0x1f5
[  252.094008]  [<ffffffff8100277b>] system_call_fastpath+0x16/0x1b
[  252.094008] Code: 05 ff c0 48 29 f7 48 39 f7 73 f6 48 89 3a c9 c3 90 90 90 8b 07 8b 16 55 89 17 48 89 e5 89 06 c9 c3 55 48 89 e5 8a 07 8a 0e ff ca <88> 0f 48 ff c7 88 06 48 ff c6 85 d2 7f ec c9 c3 55 89 d0 48 89
[  252.094008] RIP  [<ffffffff81225ee0>] generic_swap+0xa/0x1a
[  252.094008]  RSP <ffff88011a217d98>
[  252.094008] CR2: ffffffffa0680764
[  252.094008] ---[ end trace f88479be6b01e4c4 ]---


> +config DEBUG_SET_MODULE_RONX
> +	bool "Set loadable kernel module data as NX and text as RO"
> +	default n
> +	depends on X86 && MODULES

	depends on X86 && MODULES && !JUMP_LABEL

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