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Commit 825d0b73 authored by Song Liu's avatar Song Liu Committed by Thomas Gleixner
Browse files

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



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: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908282352470.1938@nanos.tec.linutronix.de
parent a55aa89a

arch/x86/mm/pti.c

+4 −2
Original line number Diff line number Diff line
@@ -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;

		}