linux-kernel - [PATCH 08/42] x86, kaslr: Get correct max

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Date:	Tue,  7 Jul 2015 13:19:54 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Kees Cook <keescook@...omium.org>,
	"H. Peter Anvin" <hpa@...or.com>, Baoquan He <bhe@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>
Subject: [PATCH 08/42] x86, kaslr: Get correct max_addr for relocs pointer

There is boundary checking for pointer in kaslr relocation handling.

Current code is using output_len, and that is VO (vmlinux after objcopy)
file size plus vmlinux.relocs file size.

That is not right, as we should use loaded address for running.

At that time parse_elf already move the sections according to ELF headers.

The valid range should be VO [_text, __bss_start) loaded physical addresses.

In the patch, add export for __bss_start to voffset.h and use it to get
max_addr.

Signed-off-by: Yinghai Lu <yinghai@...nel.org>
---
 arch/x86/boot/compressed/Makefile | 2 +-
 arch/x86/boot/compressed/misc.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 50daea7..e12a93c 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -40,7 +40,7 @@ LDFLAGS_vmlinux := -T
 hostprogs-y	:= mkpiggy
 HOST_EXTRACFLAGS += -I$(srctree)/tools/include
 
-sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
+sed-voffset := -e 's/^\([0-9a-fA-F]*\) [ABCDGRSTVW] \(_text\|__bss_start\|_end\)$$/\#define VO_\2 _AC(0x\1,UL)/p'
 
 quiet_cmd_voffset = VOFFSET $@
       cmd_voffset = $(NM) $< | sed -n $(sed-voffset) > $@
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index db97bdf..8fb74ba 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -234,7 +234,7 @@ static void handle_relocations(void *output, unsigned long output_len)
 	int *reloc;
 	unsigned long delta, map, ptr;
 	unsigned long min_addr = (unsigned long)output;
-	unsigned long max_addr = min_addr + output_len;
+	unsigned long max_addr = min_addr + (VO___bss_start - VO__text);
 
 	/*
 	 * Calculate the delta between where vmlinux was linked to load
-- 
1.8.4.5

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