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