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Subject[PATCH 4.4 28/72] arm64: avoid overflow in VA_START and PAGE_OFFSET
Date
4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nick Desaulniers <ndesaulniers@google.com>

commit 82cd588052815eb4146f9f7c5347ca5e32c56360 upstream.

The bitmask used to define these values produces overflow, as seen by
this compiler warning:

arch/arm64/kernel/head.S:47:8: warning:
integer overflow in preprocessor expression
#elif (PAGE_OFFSET & 0x1fffff) != 0
^~~~~~~~~~~
arch/arm64/include/asm/memory.h:52:46: note:
expanded from macro 'PAGE_OFFSET'
#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS -
1))
~~~~~~~~~~~~~~~~~~ ^

It would be preferrable to use GENMASK_ULL() instead, but it's not set
up to be used from assembly (the UL() macro token pastes UL suffixes
when not included in assembly sources).

Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Suggested-by: Yury Norov <ynorov@caviumnetworks.com>
Suggested-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[natechancellor: KIMAGE_VADDR doesn't exist]
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm64/include/asm/memory.h | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -49,8 +49,10 @@
* and PAGE_OFFSET - it must be within 128MB of the kernel text.
*/
#define VA_BITS (CONFIG_ARM64_VA_BITS)
-#define VA_START (UL(0xffffffffffffffff) << VA_BITS)
-#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1))
+#define VA_START (UL(0xffffffffffffffff) - \
+ (UL(1) << VA_BITS) + 1)
+#define PAGE_OFFSET (UL(0xffffffffffffffff) - \
+ (UL(1) << (VA_BITS - 1)) + 1)
#define MODULES_END (PAGE_OFFSET)
#define MODULES_VADDR (MODULES_END - SZ_64M)
#define PCI_IO_END (MODULES_VADDR - SZ_2M)

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