[PATCH V2] arm64/mm: Fix pgtable page offset address in [pud|pmd]_free_[pmd|pte]_page

[Anshuman Khandual <anshuman.khandual@arm.com>]

The pgtable page address can be fetched with [pmd|pte]_offset_[kernel] if
the input address is either PMD_SIZE or PTE_SIZE aligned. Though incoming
input addresses tend to be aligned to the required size (PMD_SIZE|PTE_SIZE)
which is the reason why there were no reported problems earlier. But it is
not correct. However 0UL as input address will guarantee that the fetched
pgtable page address is always correct without any possible skid. While at
this just warn once when the addresses are not aligned.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V2:

- Replaced WARN_ON_ONCE() with VM_WARN_ONCE() as per Catalin

 arch/arm64/mm/mmu.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index e97f018ff740..9dc1c7e90ef4 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1005,7 +1005,9 @@ int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
 		return 1;
 	}
 
-	table = pte_offset_kernel(pmdp, addr);
+	VM_WARN_ONCE(!IS_ALIGNED(addr, PMD_SIZE),
+		"%s: unaligned address: 0x%016llx\n", __func__, addr);
+	table = pte_offset_kernel(pmdp, 0UL);
 	pmd_clear(pmdp);
 	__flush_tlb_kernel_pgtable(addr);
 	pte_free_kernel(NULL, table);
@@ -1026,8 +1028,10 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
 		return 1;
 	}
 
-	table = pmd_offset(pudp, addr);
-	pmdp = table;
+	VM_WARN_ONCE(!IS_ALIGNED(addr, PUD_SIZE),
+		"%s: unaligned address 0x%016llx\n", __func__, addr);
+	table = pmd_offset(pudp, 0UL);
+	pmdp = pmd_offset(pudp, addr);
 	next = addr;
 	end = addr + PUD_SIZE;
 	do {
-- 
2.20.1


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