linux-kernel - [PATCH v4 02/20] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

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Date:	Tue, 22 Mar 2016 15:31:59 +0800
From:	Baoquan He <bhe@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	yinghai@...nel.org, keescook@...omium.org, hpa@...or.com,
	mingo@...hat.com, bp@...en8.de, vgoyal@...hat.com, luto@...nel.org,
	lasse.collin@...aani.org, akpm@...ux-foundation.org,
	dyoung@...hat.com, Baoquan He <bhe@...hat.com>
Subject: [PATCH v4 02/20] x86, kaslr: Fix a bug that relocation can not be handled when kernel is loaded above 2G

When process 32 bit relocation tables a local variable 'extended'
is defined to calculate the physical address of relocs entry.
However its type is 'int' which is enough for i386, but not enough
for x86_64. That's why relocation can only be handled under 2G.
Otherwise a overflow will happen and cause system hang.

Here change it to 'long' as 32 bit inverse relocation processing
does, and this change is safe for i386 relocation handling.

Signed-off-by: Baoquan He <bhe@...hat.com>
Acked-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 f35ad9e..c4477d5 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -295,7 +295,7 @@ 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;
-- 
2.5.0