linux-kernel - [PATCH] x86, kaslr: avoid setup

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Message-ID: <20140911161931.GA12001@www.outflux.net>
Date:	Thu, 11 Sep 2014 09:19:31 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, Baoquan He <bhe@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	Pavel Machek <pavel@....cz>
Subject: [PATCH] x86, kaslr: avoid setup_data when picking location

The KASLR location-choosing logic needs to avoid the setup_data list
memory areas as well. Without this, it would be possible to have the
ASLR position stomp on the memory, ultimately causing the boot to fail.

Signed-off-by: Kees Cook <keescook@...omium.org>
Tested-by: Baoquan He <bhe@...hat.com>
Cc: stable@...r.kernel.org
---
 arch/x86/boot/compressed/aslr.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index fc6091abedb7..d39189ba7f8e 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -183,12 +183,27 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
 static bool mem_avoid_overlap(struct mem_vector *img)
 {
 	int i;
+	struct setup_data *ptr;
 
 	for (i = 0; i < MEM_AVOID_MAX; i++) {
 		if (mem_overlaps(img, &mem_avoid[i]))
 			return true;
 	}
 
+	/* Avoid all entries in the setup_data linked list. */
+	ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
+	while (ptr) {
+		struct mem_vector avoid;
+
+		avoid.start = (u64)ptr;
+		avoid.size = sizeof(*ptr) + ptr->len;
+
+		if (mem_overlaps(img, &avoid))
+			return true;
+
+		ptr = (struct setup_data *)(unsigned long)ptr->next;
+	}
+
 	return false;
 }
 
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security
--
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