arm64: mm: Ensure tail of unaligned initrd is reserved

In the event that the start address of the initrd is not aligned, but
has an aligned size, the base + size will not cover the entire initrd
image and there is a chance that the kernel will corrupt the tail of the
image.

By aligning the end of the initrd to a page boundary and then
subtracting the adjusted start address the memblock reservation will
cover all pages that contains the initrd.

Fixes: c756c592 ("arm64: Utilize phys_initrd_start/phys_initrd_size")
Cc: stable@vger.kernel.org
Acked-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NBjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/init.c

@@ -363,7 +363,7 @@ void __init arm64_memblock_init(void)
 		 * Otherwise, this is a no-op
 		 */
 		u64 base = phys_initrd_start & PAGE_MASK;
-		u64 size = PAGE_ALIGN(phys_initrd_size);
+		u64 size = PAGE_ALIGN(phys_initrd_start + phys_initrd_size) - base;
 
 		/*
 		 * We can only add back the initrd memory if we don't end up