Commit 90de8a2f authored Sep 18, 2019 by Aneesh Kumar K.V Committed by Greg Kroah-Hartman Jan 27, 2020

powerpc/mm/mce: Keep irqs disabled during lockless page table walk



[ Upstream commit d9101bfa6adc831bda8836c4d774820553c14942 ]

__find_linux_mm_pte() returns a page table entry pointer after walking
the page table without holding locks. To make it safe against a THP
split and/or collapse, we disable interrupts around the lockless page
table walk. However we need to keep interrupts disabled as long as we
use the page table entry pointer that is returned.

Fix addr_to_pfn() to do that.

Fixes: ba41e1e1 ("powerpc/mce: Hookup derror (load/store) UE errors")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
[mpe: Rearrange code slightly and tweak change log wording]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190918145328.28602-1-aneesh.kumar@linux.ibm.com


Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 12ed084d

arch/powerpc/kernel/mce_power.c

+12 −8

Original line number	Diff line number	Diff line
		@@ -40,7 +40,7 @@ static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)
		{
		pte_t *ptep;
		unsigned int shift;
		unsigned long flags;
		unsigned long pfn, flags;
		struct mm_struct *mm;

		if (user_mode(regs))
		@@ -50,18 +50,22 @@ static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr)

		local_irq_save(flags);
		ptep = __find_linux_pte(mm->pgd, addr, NULL, &shift);
		local_irq_restore(flags);

		if (!ptep \|\| pte_special(*ptep))
		return ULONG_MAX;
		if (!ptep \|\| pte_special(*ptep)) {
		pfn = ULONG_MAX;
		goto out;
		}

		if (shift > PAGE_SHIFT) {
		if (shift <= PAGE_SHIFT)
		pfn = pte_pfn(*ptep);
		else {
		unsigned long rpnmask = (1ul << shift) - PAGE_SIZE;

		return pte_pfn(__pte(pte_val(*ptep) \| (addr & rpnmask)));
		pfn = pte_pfn(__pte(pte_val(*ptep) \| (addr & rpnmask)));
		}

		return pte_pfn(*ptep);
		out:
		local_irq_restore(flags);
		return pfn;
		}

		/* flush SLBs and reload */