linux-kernel - [PATCH] x86/KASLR: move aligning of minimal address to choose_random

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Date:   Thu,  4 Jan 2018 15:54:21 +0600
From:   Alexander Kuleshov <kuleshovmail@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Baoquan He <bhe@...hat.com>, Kees Cook <keescook@...omium.org>,
        Dave Jiang <dave.jiang@...el.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Alexander Kuleshov <kuleshovmail@...il.com>
Subject: [PATCH] x86/KASLR: move aligning of minimal address to choose_random_location()

we align minimal possible address during randomization to CONFIG_PHYSICAL_ALIGN
two times: during getting of random physical address and virtual
address (only for x86_64).

Let's move this to choose_random_location() to not duplicate code in
find_random_virt_addr() and find_random_phys_addr().

Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
---
 arch/x86/boot/compressed/kaslr.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 8199a6187251..8c93e399fdfd 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -673,9 +673,6 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
 		return 0;
 	}
 
-	/* Make sure minimum is aligned. */
-	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
-
 	if (process_efi_entries(minimum, image_size))
 		return slots_fetch_random();
 
@@ -688,8 +685,6 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
 {
 	unsigned long slots, random_addr;
 
-	/* Make sure minimum is aligned. */
-	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
 	/* Align image_size for easy slot calculations. */
 	image_size = ALIGN(image_size, CONFIG_PHYSICAL_ALIGN);
 
@@ -738,6 +733,9 @@ void choose_random_location(unsigned long input,
 	 */
 	min_addr = min(*output, 512UL << 20);
 
+	/* Make sure minimum is aligned. */
+	min_addr = ALIGN(min_addr, CONFIG_PHYSICAL_ALIGN);
+
 	/* Walk available memory entries to find a random address. */
 	random_addr = find_random_phys_addr(min_addr, output_size);
 	if (!random_addr) {
-- 
2.14.3