[PATCH v3 06/23] KVM: arm64: Reject zero-sized ranges in pfn_range_is_valid()

[Vincent Donnefort]

pfn_range_is_valid() validates that a [pfn, pfn + nr_pages) range fits
within the physical address space, but does nothing when nr_pages is 0.

Luckily, there's currently no existing check that could be evaded.
However the pfn_range_is_valid() should make size trustworthy and 0
could be problematic. Explicitly reject 0 range size.

Signed-off-by: Vincent Donnefort <vdonnefort at google.com>
---
 arch/arm64/kvm/hyp/nvhe/mem_protect.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
index 8d5bfae67396..385a7ed12b3c 100644
--- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
+++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
@@ -400,6 +400,9 @@ static bool pfn_range_is_valid(u64 pfn, u64 nr_pages)
 {
 	u64 limit = BIT(kvm_phys_shift(&host_mmu.arch.mmu) - PAGE_SHIFT);
 
+	if (!nr_pages)
+		return false;
+
 	return pfn < limit && ((limit - pfn) >= nr_pages);
 }
 
-- 
2.56.0.385.gac671c819a-goog