[PATCH v2] ARM: mm: fix size rounding-down of arm_add_memory() function
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From: Ard Biesheuvel <hidden>
Date: 2014-12-22 09:09:35
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On 22 December 2014 at 04:17, Masahiro Yamada [off-list ref] wrote:
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 <redacted> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Ard Biesheuvel <redacted>
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--- 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