forked from rpms/kernel
49 lines
1.5 KiB
Diff
49 lines
1.5 KiB
Diff
From: Samu Kallio <>
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Subject: [PATCH] x86: mm: Fix vmalloc_fault oops during lazy MMU updates.
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Date: Sun, 17 Feb 2013 04:35:52 +0200
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In paravirtualized x86_64 kernels, vmalloc_fault may cause an oops
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when lazy MMU updates are enabled, because set_pgd effects are being
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deferred.
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One instance of this problem is during process mm cleanup with memory
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cgroups enabled. The chain of events is as follows:
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- zap_pte_range enables lazy MMU updates
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- zap_pte_range eventually calls mem_cgroup_charge_statistics,
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which accesses the vmalloc'd mem_cgroup per-cpu stat area
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- vmalloc_fault is triggered which tries to sync the corresponding
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PGD entry with set_pgd, but the update is deferred
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- vmalloc_fault oopses due to a mismatch in the PUD entries
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Calling arch_flush_lazy_mmu_mode immediately after set_pgd makes the
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changes visible to the consistency checks.
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Signed-off-by: Samu Kallio <samu.kallio@aberdeencloud.com>
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---
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arch/x86/mm/fault.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
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index 8e13ecb..0a45298 100644
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--- a/arch/x86/mm/fault.c
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+++ b/arch/x86/mm/fault.c
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@@ -378,10 +378,12 @@ static noinline __kprobes int vmalloc_fault(unsigned long address)
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if (pgd_none(*pgd_ref))
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return -1;
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- if (pgd_none(*pgd))
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+ if (pgd_none(*pgd)) {
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set_pgd(pgd, *pgd_ref);
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- else
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+ arch_flush_lazy_mmu_mode();
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+ } else {
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BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
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+ }
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/*
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* Below here mismatches are bugs because these lower tables
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--
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1.8.1.3
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