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x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable()

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pti_clone_pmds() assumes that the supplied address is either:

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

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

[ tglx: Rewrote changelog and added WARN_ON_ONCE() ]

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908282352470.1938@nanos.tec.linutronix.de
This commit is contained in:
Song Liu 2019-08-28 23:54:55 +02:00 committed by Thomas Gleixner
parent a55aa89aab
commit 825d0b73cd
1 changed files with 4 additions and 2 deletions
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6
arch/x86/mm/pti.c
View file

@ -330,13 +330,15 @@ pti_clone_pgtable(unsigned long start, unsigned long end,
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;
}