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

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Message-ID: <20140514074940.GA18774@dhcp-16-198.nay.redhat.com>
Date:	Wed, 14 May 2014 15:49:40 +0800
From:	Dave Young <dyoung@...hat.com>
To:	keescook@...omium.org, hpa@...or.com, linux-kernel@...r.kernel.org
Subject: [PATCH] x86: kaslr to avoid setup_data regions

X86 will pass setup_data region while necessary, these regions could be
overwitten by kernel due to kaslr.

Thus iterate and add setup regions to mem_avoid[] in this patch.
Set max mem avoid entries 32, hopefully it will be enough.

Signed-off-by: Dave Young <dyoung@...hat.com>
---
 arch/x86/boot/compressed/aslr.c |   28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

Index: linux-2.6/arch/x86/boot/compressed/aslr.c
===================================================================
--- linux-2.6.orig/arch/x86/boot/compressed/aslr.c
+++ linux-2.6/arch/x86/boot/compressed/aslr.c
@@ -110,8 +110,9 @@ struct mem_vector {
 	unsigned long size;
 };
 
-#define MEM_AVOID_MAX 5
+#define MEM_AVOID_MAX 32
 static struct mem_vector mem_avoid[MEM_AVOID_MAX];
+static int mem_avoid_nr;
 
 static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
 {
@@ -135,6 +136,28 @@ static bool mem_overlaps(struct mem_vect
 	return true;
 }
 
+static void mem_avoid_setup_data(void)
+{
+	struct setup_data *data;
+	u64 pa_data;
+
+	if (mem_avoid_nr >= MEM_AVOID_MAX) {
+		debug_putstr("KASLR: too many setup_data ranges.\n");
+		return;
+	}
+
+	pa_data = real_mode->hdr.setup_data;
+	while (pa_data) {
+		data = (struct setup_data *)pa_data;
+		if (pa_data < CONFIG_RANDOMIZE_BASE_MAX_OFFSET) {
+			mem_avoid[mem_avoid_nr].start = pa_data;
+			mem_avoid[mem_avoid_nr].size = sizeof(*data) + data->len;
+			mem_avoid_nr++;
+		}
+		pa_data = data->next;
+	}
+}
+
 static void mem_avoid_init(unsigned long input, unsigned long input_size,
 			   unsigned long output, unsigned long output_size)
 {
@@ -177,6 +200,9 @@ static void mem_avoid_init(unsigned long
 	/* Avoid stack memory. */
 	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
 	mem_avoid[4].size = BOOT_STACK_SIZE;
+	mem_avoid_nr = 5;
+
+	mem_avoid_setup_data();
 }
 
 /* Does this memory vector overlap a known avoided area? */
--
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