From: Huang Ying <ying.huang@xxxxxxxxx>
Subject: mm: fix races between swapoff and flush dcache
Thanks to 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks"),
after swapoff the address_space associated with the swap device will be
freed. So page_mapping() users which may touch the address_space need
some kind of mechanism to prevent the address_space from being freed
during accessing.
The dcache flushing functions (flush_dcache_page(), etc) in architecture
specific code may access the address_space of swap device for anonymous
pages in swap cache via page_mapping() function. But in some cases there
are no mechanisms to prevent the swap device from being swapoff, for
example,
CPU1 CPU2
__get_user_pages() swapoff()
flush_dcache_page()
mapping = page_mapping()
... exit_swap_address_space()
... kvfree(spaces)
mapping_mapped(mapping)
The address space may be accessed after being freed.
But from cachetlb.txt and Russell King, flush_dcache_page() only care
about file cache pages, for anonymous pages, flush_anon_page() should be
used. The implementation of flush_dcache_page() in all architectures
follows this too. They will check whether page_mapping() is NULL and
whether mapping_mapped() is true to determine whether to flush the dcache
immediately. And they will use interval tree (mapping->i_mmap) to find
all user space mappings. While mapping_mapped() and mapping->i_mmap isn't
used by anonymous pages in swap cache at all.
So, to fix the race between swapoff and flush dcache, __page_mapping() is
add to return the address_space for file cache pages and NULL otherwise.
All page_mapping() invoking in flush dcache functions are replaced with
page_mapping_file().
[akpm@xxxxxxxxxxxxxxxxxxxx: simplify page_mapping_file(), per Mike]
Link: http://lkml.kernel.org/r/20180305083634.15174-1-ying.huang@xxxxxxxxx
Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Chen Liqin <liqin.linux@xxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxx>
Cc: Guan Xuetao <gxt@xxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Chris Zankel <chris@xxxxxxxxxx>
Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Cc: Ley Foon Tan <lftan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arc/mm/cache.c | 2 +-
arch/arm/mm/copypage-v4mc.c | 2 +-
arch/arm/mm/copypage-v6.c | 2 +-
arch/arm/mm/copypage-xscale.c | 2 +-
arch/arm/mm/fault-armv.c | 2 +-
arch/arm/mm/flush.c | 6 +++---
arch/mips/mm/cache.c | 2 +-
arch/nios2/mm/cacheflush.c | 4 ++--
arch/parisc/kernel/cache.c | 5 +++--
arch/sh/mm/cache-sh4.c | 2 +-
arch/sh/mm/cache-sh7705.c | 2 +-
arch/sparc/kernel/smp_64.c | 8 ++++----
arch/sparc/mm/init_64.c | 6 +++---
arch/sparc/mm/tlb.c | 2 +-
arch/unicore32/mm/flush.c | 2 +-
arch/unicore32/mm/mmu.c | 2 +-
arch/xtensa/mm/cache.c | 2 +-
include/linux/mm.h | 1 +
mm/util.c | 10 ++++++++++
19 files changed, 38 insertions(+), 26 deletions(-)
diff -puN arch/arc/mm/cache.c~mm-fix-races-between-swapoff-and-flush-dcache arch/arc/mm/cache.c
--- a/arch/arc/mm/cache.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/arc/mm/cache.c
@@ -833,7 +833,7 @@ void flush_dcache_page(struct page *page
}
/* don't handle anon pages here */
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!mapping)
return;
diff -puN arch/arm/mm/copypage-v4mc.c~mm-fix-races-between-swapoff-and-flush-dcache arch/arm/mm/copypage-v4mc.c
--- a/arch/arm/mm/copypage-v4mc.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/arm/mm/copypage-v4mc.c
@@ -70,7 +70,7 @@ void v4_mc_copy_user_highpage(struct pag
void *kto = kmap_atomic(to);
if (!test_and_set_bit(PG_dcache_clean, &from->flags))
- __flush_dcache_page(page_mapping(from), from);
+ __flush_dcache_page(page_mapping_file(from), from);
raw_spin_lock(&minicache_lock);
diff -puN arch/arm/mm/copypage-v6.c~mm-fix-races-between-swapoff-and-flush-dcache arch/arm/mm/copypage-v6.c
--- a/arch/arm/mm/copypage-v6.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/arm/mm/copypage-v6.c
@@ -76,7 +76,7 @@ static void v6_copy_user_highpage_aliasi
unsigned long kfrom, kto;
if (!test_and_set_bit(PG_dcache_clean, &from->flags))
- __flush_dcache_page(page_mapping(from), from);
+ __flush_dcache_page(page_mapping_file(from), from);
/* FIXME: not highmem safe */
discard_old_kernel_data(page_address(to));
diff -puN arch/arm/mm/copypage-xscale.c~mm-fix-races-between-swapoff-and-flush-dcache arch/arm/mm/copypage-xscale.c
--- a/arch/arm/mm/copypage-xscale.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/arm/mm/copypage-xscale.c
@@ -90,7 +90,7 @@ void xscale_mc_copy_user_highpage(struct
void *kto = kmap_atomic(to);
if (!test_and_set_bit(PG_dcache_clean, &from->flags))
- __flush_dcache_page(page_mapping(from), from);
+ __flush_dcache_page(page_mapping_file(from), from);
raw_spin_lock(&minicache_lock);
diff -puN arch/arm/mm/fault-armv.c~mm-fix-races-between-swapoff-and-flush-dcache arch/arm/mm/fault-armv.c
--- a/arch/arm/mm/fault-armv.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/arm/mm/fault-armv.c
@@ -195,7 +195,7 @@ void update_mmu_cache(struct vm_area_str
if (page == ZERO_PAGE(0))
return;
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!test_and_set_bit(PG_dcache_clean, &page->flags))
__flush_dcache_page(mapping, page);
if (mapping) {
diff -puN arch/arm/mm/flush.c~mm-fix-races-between-swapoff-and-flush-dcache arch/arm/mm/flush.c
--- a/arch/arm/mm/flush.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/arm/mm/flush.c
@@ -285,7 +285,7 @@ void __sync_icache_dcache(pte_t pteval)
page = pfn_to_page(pfn);
if (cache_is_vipt_aliasing())
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
else
mapping = NULL;
@@ -333,7 +333,7 @@ void flush_dcache_page(struct page *page
return;
}
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!cache_ops_need_broadcast() &&
mapping && !page_mapcount(page))
@@ -363,7 +363,7 @@ void flush_kernel_dcache_page(struct pag
if (cache_is_vivt() || cache_is_vipt_aliasing()) {
struct address_space *mapping;
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!mapping || mapping_mapped(mapping)) {
void *addr;
diff -puN arch/mips/mm/cache.c~mm-fix-races-between-swapoff-and-flush-dcache arch/mips/mm/cache.c
--- a/arch/mips/mm/cache.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/mips/mm/cache.c
@@ -86,7 +86,7 @@ SYSCALL_DEFINE3(cacheflush, unsigned lon
void __flush_dcache_page(struct page *page)
{
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping = page_mapping_file(page);
unsigned long addr;
if (mapping && !mapping_mapped(mapping)) {
diff -puN arch/nios2/mm/cacheflush.c~mm-fix-races-between-swapoff-and-flush-dcache arch/nios2/mm/cacheflush.c
--- a/arch/nios2/mm/cacheflush.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/nios2/mm/cacheflush.c
@@ -180,7 +180,7 @@ void flush_dcache_page(struct page *page
if (page == ZERO_PAGE(0))
return;
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
/* Flush this page if there are aliases. */
if (mapping && !mapping_mapped(mapping)) {
@@ -215,7 +215,7 @@ void update_mmu_cache(struct vm_area_str
if (page == ZERO_PAGE(0))
return;
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!test_and_set_bit(PG_dcache_clean, &page->flags))
__flush_dcache_page(mapping, page);
diff -puN arch/parisc/kernel/cache.c~mm-fix-races-between-swapoff-and-flush-dcache arch/parisc/kernel/cache.c
--- a/arch/parisc/kernel/cache.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/parisc/kernel/cache.c
@@ -88,7 +88,8 @@ update_mmu_cache(struct vm_area_struct *
return;
page = pfn_to_page(pfn);
- if (page_mapping(page) && test_bit(PG_dcache_dirty, &page->flags)) {
+ if (page_mapping_file(page) &&
+ test_bit(PG_dcache_dirty, &page->flags)) {
flush_kernel_dcache_page_addr(pfn_va(pfn));
clear_bit(PG_dcache_dirty, &page->flags);
} else if (parisc_requires_coherency())
@@ -304,7 +305,7 @@ __flush_cache_page(struct vm_area_struct
void flush_dcache_page(struct page *page)
{
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping = page_mapping_file(page);
struct vm_area_struct *mpnt;
unsigned long offset;
unsigned long addr, old_addr = 0;
diff -puN arch/sh/mm/cache-sh4.c~mm-fix-races-between-swapoff-and-flush-dcache arch/sh/mm/cache-sh4.c
--- a/arch/sh/mm/cache-sh4.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/sh/mm/cache-sh4.c
@@ -112,7 +112,7 @@ static void sh4_flush_dcache_page(void *
struct page *page = arg;
unsigned long addr = (unsigned long)page_address(page);
#ifndef CONFIG_SMP
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping = page_mapping_file(page);
if (mapping && !mapping_mapped(mapping))
clear_bit(PG_dcache_clean, &page->flags);
diff -puN arch/sh/mm/cache-sh7705.c~mm-fix-races-between-swapoff-and-flush-dcache arch/sh/mm/cache-sh7705.c
--- a/arch/sh/mm/cache-sh7705.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/sh/mm/cache-sh7705.c
@@ -136,7 +136,7 @@ static void __flush_dcache_page(unsigned
static void sh7705_flush_dcache_page(void *arg)
{
struct page *page = arg;
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping = page_mapping_file(page);
if (mapping && !mapping_mapped(mapping))
clear_bit(PG_dcache_clean, &page->flags);
diff -puN arch/sparc/kernel/smp_64.c~mm-fix-races-between-swapoff-and-flush-dcache arch/sparc/kernel/smp_64.c
--- a/arch/sparc/kernel/smp_64.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/sparc/kernel/smp_64.c
@@ -929,9 +929,9 @@ static inline void __local_flush_dcache_
#ifdef DCACHE_ALIASING_POSSIBLE
__flush_dcache_page(page_address(page),
((tlb_type == spitfire) &&
- page_mapping(page) != NULL));
+ page_mapping_file(page) != NULL));
#else
- if (page_mapping(page) != NULL &&
+ if (page_mapping_file(page) != NULL &&
tlb_type == spitfire)
__flush_icache_page(__pa(page_address(page)));
#endif
@@ -958,7 +958,7 @@ void smp_flush_dcache_page_impl(struct p
if (tlb_type == spitfire) {
data0 = ((u64)&xcall_flush_dcache_page_spitfire);
- if (page_mapping(page) != NULL)
+ if (page_mapping_file(page) != NULL)
data0 |= ((u64)1 << 32);
} else if (tlb_type == cheetah || tlb_type == cheetah_plus) {
#ifdef DCACHE_ALIASING_POSSIBLE
@@ -994,7 +994,7 @@ void flush_dcache_page_all(struct mm_str
pg_addr = page_address(page);
if (tlb_type == spitfire) {
data0 = ((u64)&xcall_flush_dcache_page_spitfire);
- if (page_mapping(page) != NULL)
+ if (page_mapping_file(page) != NULL)
data0 |= ((u64)1 << 32);
} else if (tlb_type == cheetah || tlb_type == cheetah_plus) {
#ifdef DCACHE_ALIASING_POSSIBLE
diff -puN arch/sparc/mm/init_64.c~mm-fix-races-between-swapoff-and-flush-dcache arch/sparc/mm/init_64.c
--- a/arch/sparc/mm/init_64.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/sparc/mm/init_64.c
@@ -206,9 +206,9 @@ inline void flush_dcache_page_impl(struc
#ifdef DCACHE_ALIASING_POSSIBLE
__flush_dcache_page(page_address(page),
((tlb_type == spitfire) &&
- page_mapping(page) != NULL));
+ page_mapping_file(page) != NULL));
#else
- if (page_mapping(page) != NULL &&
+ if (page_mapping_file(page) != NULL &&
tlb_type == spitfire)
__flush_icache_page(__pa(page_address(page)));
#endif
@@ -490,7 +490,7 @@ void flush_dcache_page(struct page *page
this_cpu = get_cpu();
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (mapping && !mapping_mapped(mapping)) {
int dirty = test_bit(PG_dcache_dirty, &page->flags);
if (dirty) {
diff -puN arch/sparc/mm/tlb.c~mm-fix-races-between-swapoff-and-flush-dcache arch/sparc/mm/tlb.c
--- a/arch/sparc/mm/tlb.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/sparc/mm/tlb.c
@@ -128,7 +128,7 @@ void tlb_batch_add(struct mm_struct *mm,
goto no_cache_flush;
/* A real file page? */
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!mapping)
goto no_cache_flush;
diff -puN arch/unicore32/mm/flush.c~mm-fix-races-between-swapoff-and-flush-dcache arch/unicore32/mm/flush.c
--- a/arch/unicore32/mm/flush.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/unicore32/mm/flush.c
@@ -83,7 +83,7 @@ void flush_dcache_page(struct page *page
if (page == ZERO_PAGE(0))
return;
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (mapping && !mapping_mapped(mapping))
clear_bit(PG_dcache_clean, &page->flags);
diff -puN arch/unicore32/mm/mmu.c~mm-fix-races-between-swapoff-and-flush-dcache arch/unicore32/mm/mmu.c
--- a/arch/unicore32/mm/mmu.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/unicore32/mm/mmu.c
@@ -503,7 +503,7 @@ void update_mmu_cache(struct vm_area_str
if (page == ZERO_PAGE(0))
return;
- mapping = page_mapping(page);
+ mapping = page_mapping_file(page);
if (!test_and_set_bit(PG_dcache_clean, &page->flags))
__flush_dcache_page(mapping, page);
if (mapping)
diff -puN arch/xtensa/mm/cache.c~mm-fix-races-between-swapoff-and-flush-dcache arch/xtensa/mm/cache.c
--- a/arch/xtensa/mm/cache.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/arch/xtensa/mm/cache.c
@@ -127,7 +127,7 @@ EXPORT_SYMBOL(copy_user_highpage);
void flush_dcache_page(struct page *page)
{
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping = page_mapping_file(page);
/*
* If we have a mapping but the page is not mapped to user-space
diff -puN include/linux/mm.h~mm-fix-races-between-swapoff-and-flush-dcache include/linux/mm.h
--- a/include/linux/mm.h~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/include/linux/mm.h
@@ -1155,6 +1155,7 @@ static inline pgoff_t page_index(struct
bool page_mapped(struct page *page);
struct address_space *page_mapping(struct page *page);
+struct address_space *page_mapping_file(struct page *page);
/*
* Return true only if the page has been allocated with
diff -puN mm/util.c~mm-fix-races-between-swapoff-and-flush-dcache mm/util.c
--- a/mm/util.c~mm-fix-races-between-swapoff-and-flush-dcache
+++ a/mm/util.c
@@ -515,6 +515,16 @@ struct address_space *page_mapping(struc
}
EXPORT_SYMBOL(page_mapping);
+/*
+ * For file cache pages, return the address_space, otherwise return NULL
+ */
+struct address_space *page_mapping_file(struct page *page)
+{
+ if (unlikely(PageSwapCache(page)))
+ return NULL;
+ return page_mapping(page);
+}
+
/* Slow path of page_mapcount() for compound pages */
int __page_mapcount(struct page *page)
{
_
--
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