arm64/mm: Validate hotplug range before creating linear mapping

During memory hotplug process, the linear mapping should not be created for
a given memory range if that would fall outside the maximum allowed linear
range. Else it might cause memory corruption in the kernel virtual space.

Maximum linear mapping region is [PAGE_OFFSET..(PAGE_END -1)] accommodating
both its ends but excluding PAGE_END. Max physical range that can be mapped
inside this linear mapping range, must also be derived from its end points.

This ensures that arch_add_memory() validates memory hot add range for its
potential linear mapping requirements, before creating it with
__create_pgd_mapping().

Fixes: 4ab215061554 ("arm64: Add memory hotplug support")
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Link: https://lore.kernel.org/r/1605252614-761-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 1c0f3e02f731edd8b962b2d62a8954236b91c3d7..ca692a8157315dda46557a3962cc3df6d121f439 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1444,11 +1444,28 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size)
        free_empty_tables(start, end, PAGE_OFFSET, PAGE_END);
 }
 
+static bool inside_linear_region(u64 start, u64 size)
+{
+       /*
+        * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)]
+        * accommodating both its ends but excluding PAGE_END. Max physical
+        * range which can be mapped inside this linear mapping range, must
+        * also be derived from its end points.
+        */
+       return start >= __pa(_PAGE_OFFSET(vabits_actual)) &&
+              (start + size - 1) <= __pa(PAGE_END - 1);
+}
+
 int arch_add_memory(int nid, u64 start, u64 size,
                    struct mhp_params *params)
 {
        int ret, flags = 0;
 
+       if (!inside_linear_region(start, size)) {
+               pr_err("[%llx %llx] is outside linear mapping region\n", start, start + size);
+               return -EINVAL;
+       }
+
        if (rodata_full || debug_pagealloc_enabled())
                flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;