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Subject[patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable()
From: Song Liu <songliubraving@fb.com>

pti_clone_pmds() assumes that the supplied address is either:

- properly PUD/PMD aligned
or
- the address is actually mapped which means that independent
of the mapping level (PUD/PMD/PTE) the next higher mapping
exist.

If that's not the case the unaligned address can be incremented by PUD or
PMD size wrongly. All callers supply mapped and/or aligned addresses, but
for robustness sake, it's better to handle that case proper and to emit a
warning.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190820202314.1083149-1-songliubraving@fb.com

---
arch/x86/mm/pti.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -330,13 +330,15 @@ pti_clone_pgtable(unsigned long start, u

pud = pud_offset(p4d, addr);
if (pud_none(*pud)) {
- addr += PUD_SIZE;
+ WARN_ON_ONCE(addr & PUD_MASK);
+ addr = round_up(addr + 1, PUD_SIZE);
continue;
}

pmd = pmd_offset(pud, addr);
if (pmd_none(*pmd)) {
- addr += PMD_SIZE;
+ WARN_ON_ONCE(addr & PMD_MASK);
+ addr = round_up(addr + 1, PMD_SIZE);
continue;
}


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