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Subject[PATCH v2] ARM: mm: fix size rounding-down of arm_add_memory() function
Date
The current rounding of "size" is wrong:

- If "start" is sufficiently near the next page boundary, "size"
is decremented by more than enough and the last page is lost.

- If "size" is sufficiently small, it is wrapped around and gets
a bogus value.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
---

Changes in v2:
- Avoid wrap around of "size"

arch/arm/kernel/setup.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index f9c8639..d13f185 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -657,10 +657,13 @@ int __init arm_add_memory(u64 start, u64 size)

/*
* Ensure that start/size are aligned to a page boundary.
- * Size is appropriately rounded down, start is rounded up.
+ * Size is rounded down, start is rounded up.
*/
- size -= start & ~PAGE_MASK;
aligned_start = PAGE_ALIGN(start);
+ if (aligned_start > start + size)
+ size = 0;
+ else
+ size -= aligned_start - start;

#ifndef CONFIG_ARCH_PHYS_ADDR_T_64BIT
if (aligned_start > ULONG_MAX) {
--
1.9.1


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