ARM: 7931/1: Correct virt_addr_valid

The definition of virt_addr_valid is that virt_addr_valid should
return true if and only if virt_to_page returns a valid pointer.
The current definition of virt_addr_valid only checks against the
virtual address range. There's no guarantee that just because a
virtual address falls bewteen PAGE_OFFSET and high_memory the
associated physical memory has a valid backing struct page. Follow
the example of other architectures and convert to pfn_valid to
verify that the virtual address is actually valid. The check for
an address between PAGE_OFFSET and high_memory is still necessary
as vmalloc/highmem addresses are not valid with virt_to_page.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Nicolas Pitre <nico@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/memory.h

@@ -347,7 +347,8 @@ static inline __deprecated void *bus_to_virt(unsigned long x)
 #define ARCH_PFN_OFFSET		PHYS_PFN_OFFSET
 
 #define virt_to_page(kaddr)	pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
-#define virt_addr_valid(kaddr)	((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory)
+#define virt_addr_valid(kaddr)	(((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory) \
+					&& pfn_valid(__pa(kaddr) >> PAGE_SHIFT) )
 
 #endif