[PATCH] of: check for size < 0 after rounding in early_init_dt_add_memory_arch

[PATCH] of: check for size < 0 after rounding in early_init_dt_add_memory_arch

[Ard Biesheuvel]

Memory regions passed to early_init_dt_add_memory_arch() are rounded to
PAGE_SIZE by subtracting the size of the leading fractional page from
the 'size' argument. However, size being a u64 type, if its value is
sufficiently small, the subtraction wraps around and produces a bogus
value, potentially leading to crashes.

Fix this by ignoring the memory range in such cases.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/of/fdt.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index d1ffca8b34ea..3b423f5b99c6 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -930,6 +930,11 @@ void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
 	const u64 phys_offset = __pa(PAGE_OFFSET);
 
 	if (!PAGE_ALIGNED(base)) {
+		if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {
+			pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
+				base, base + size);
+			return;
+		}
 		size -= PAGE_SIZE - (base & ~PAGE_MASK);
 		base = PAGE_ALIGN(base);
 	}
-- 
1.8.3.2

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Re: [PATCH] of: check for size < 0 after rounding in early_init_dt_add_memory_arch

[Grant Likely]

On Wed, 29 Oct 2014 17:09:32 +0100
, Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
 wrote:
> Memory regions passed to early_init_dt_add_memory_arch() are rounded to
> PAGE_SIZE by subtracting the size of the leading fractional page from
> the 'size' argument. However, size being a u64 type, if its value is
> sufficiently small, the subtraction wraps around and produces a bogus
> value, potentially leading to crashes.
> 
> Fix this by ignoring the memory range in such cases.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Applied, thanks.

g.

> ---
>  drivers/of/fdt.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index d1ffca8b34ea..3b423f5b99c6 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -930,6 +930,11 @@ void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
>  	const u64 phys_offset = __pa(PAGE_OFFSET);
>  
>  	if (!PAGE_ALIGNED(base)) {
> +		if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {
> +			pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
> +				base, base + size);
> +			return;
> +		}
>  		size -= PAGE_SIZE - (base & ~PAGE_MASK);
>  		base = PAGE_ALIGN(base);
>  	}
> -- 
> 1.8.3.2
> 

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