linux-kernel - [PATCH 1/6] x86/KASLR: Handle kernel relocation above 2G

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Message-Id: <1461888548-32439-2-git-send-email-keescook@chromium.org>
Date:	Thu, 28 Apr 2016 17:09:03 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Kees Cook <keescook@...omium.org>, Baoquan He <bhe@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andy Lutomirski <luto@...nel.org>, lasse.collin@...aani.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Young <dyoung@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/6] x86/KASLR: Handle kernel relocation above 2G

From: Baoquan He <bhe@...hat.com>

When processing the relocation table, the offset used to calculate the
relocation is an int. This is sufficient for calculating the physical
address of the relocs entry on 32-bit systems and on 64-bit systems when
the relocation is under 2G. To handle relocations above 2G (seen in
situations like kexec, netboot, etc), this offset needs to be calculated
using a long to avoid wrapping and miscalculating the relocation.

Signed-off-by: Baoquan He <bhe@...hat.com>
[kees: rewrote changelog]
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/boot/compressed/misc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 6dde6ccdf00e..45145149c07d 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -232,7 +232,7 @@ static void handle_relocations(void *output, unsigned long output_len)
 	 * So we work backwards from the end of the decompressed image.
 	 */
 	for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) {
-		int extended = *reloc;
+		long extended = *reloc;
 		extended += map;
 
 		ptr = (unsigned long)extended;
-- 
2.6.3