The patch titled
mm: fix race in kunmap_atomic()
has been added to the -mm tree. Its filename is
mm-fix-race-in-kunmap_atomic.patch
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------------------------------------------------------
Subject: mm: fix race in kunmap_atomic()
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Christoph reported a nice splat which illustrated a race in the new stack
based kmap_atomic implementation.
The problem is that we pop our stack slot before we're completely done
resetting its state -- in particular clearing the PTE (sometimes that's
CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear
the PTE used for the last slot, that interrupt can reuse the slot in a
dirty state, which triggers a BUG in kmap_atomic().
Fix this by introducing kmap_atomic_idx() which reports the current slot
index without actually releasing it and use that to find the PTE and delay
the _pop() until after we're completely done.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Reported-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/mm/highmem.c | 3 ++-
arch/frv/mm/highmem.c | 3 ++-
arch/mips/mm/highmem.c | 3 ++-
arch/mn10300/include/asm/highmem.h | 4 +++-
arch/powerpc/mm/highmem.c | 4 +++-
arch/sparc/mm/highmem.c | 4 +++-
arch/tile/mm/highmem.c | 3 ++-
arch/x86/mm/highmem_32.c | 3 ++-
arch/x86/mm/iomap_32.c | 3 ++-
include/linux/highmem.h | 5 +++++
10 files changed, 26 insertions(+), 9 deletions(-)
diff -puN arch/arm/mm/highmem.c~mm-fix-race-in-kunmap_atomic arch/arm/mm/highmem.c
--- a/arch/arm/mm/highmem.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/arm/mm/highmem.c
@@ -89,7 +89,7 @@ void __kunmap_atomic(void *kvaddr)
int idx, type;
if (kvaddr >= (void *)FIXADDR_START) {
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
idx = type + KM_TYPE_NR * smp_processor_id();
if (cache_is_vivt())
@@ -101,6 +101,7 @@ void __kunmap_atomic(void *kvaddr)
#else
(void) idx; /* to kill a warning */
#endif
+ kmap_atomic_idx_pop();
} else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
/* this address was obtained through kmap_high_get() */
kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
diff -puN arch/frv/mm/highmem.c~mm-fix-race-in-kunmap_atomic arch/frv/mm/highmem.c
--- a/arch/frv/mm/highmem.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/frv/mm/highmem.c
@@ -68,7 +68,7 @@ EXPORT_SYMBOL(__kmap_atomic);
void __kunmap_atomic(void *kvaddr)
{
- int type = kmap_atomic_idx_pop();
+ int type = kmap_atomic_idx();
switch (type) {
case 0: __kunmap_atomic_primary(4, 6); break;
case 1: __kunmap_atomic_primary(5, 7); break;
@@ -83,6 +83,7 @@ void __kunmap_atomic(void *kvaddr)
default:
BUG();
}
+ kmap_atomic_idx_pop();
pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);
diff -puN arch/mips/mm/highmem.c~mm-fix-race-in-kunmap_atomic arch/mips/mm/highmem.c
--- a/arch/mips/mm/highmem.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/mips/mm/highmem.c
@@ -74,7 +74,7 @@ void __kunmap_atomic(void *kvaddr)
return;
}
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
#ifdef CONFIG_DEBUG_HIGHMEM
{
int idx = type + KM_TYPE_NR * smp_processor_id();
@@ -89,6 +89,7 @@ void __kunmap_atomic(void *kvaddr)
local_flush_tlb_one(vaddr);
}
#endif
+ kmap_atomic_idx_pop();
pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);
diff -puN arch/mn10300/include/asm/highmem.h~mm-fix-race-in-kunmap_atomic arch/mn10300/include/asm/highmem.h
--- a/arch/mn10300/include/asm/highmem.h~mm-fix-race-in-kunmap_atomic
+++ a/arch/mn10300/include/asm/highmem.h
@@ -101,7 +101,7 @@ static inline void __kunmap_atomic(unsig
return;
}
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
#if HIGHMEM_DEBUG
{
@@ -119,6 +119,8 @@ static inline void __kunmap_atomic(unsig
__flush_tlb_one(vaddr);
}
#endif
+
+ kmap_atomic_idx_pop();
pagefault_enable();
}
#endif /* __KERNEL__ */
diff -puN arch/powerpc/mm/highmem.c~mm-fix-race-in-kunmap_atomic arch/powerpc/mm/highmem.c
--- a/arch/powerpc/mm/highmem.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/powerpc/mm/highmem.c
@@ -62,7 +62,7 @@ void __kunmap_atomic(void *kvaddr)
return;
}
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
#ifdef CONFIG_DEBUG_HIGHMEM
{
@@ -79,6 +79,8 @@ void __kunmap_atomic(void *kvaddr)
local_flush_tlb_page(NULL, vaddr);
}
#endif
+
+ kmap_atomic_idx_pop();
pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);
diff -puN arch/sparc/mm/highmem.c~mm-fix-race-in-kunmap_atomic arch/sparc/mm/highmem.c
--- a/arch/sparc/mm/highmem.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/sparc/mm/highmem.c
@@ -75,7 +75,7 @@ void __kunmap_atomic(void *kvaddr)
return;
}
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
#ifdef CONFIG_DEBUG_HIGHMEM
{
@@ -104,6 +104,8 @@ void __kunmap_atomic(void *kvaddr)
#endif
}
#endif
+
+ kmap_atomic_idx_pop();
pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);
diff -puN arch/tile/mm/highmem.c~mm-fix-race-in-kunmap_atomic arch/tile/mm/highmem.c
--- a/arch/tile/mm/highmem.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/tile/mm/highmem.c
@@ -241,7 +241,7 @@ void __kunmap_atomic(void *kvaddr)
pte_t pteval = *pte;
int idx, type;
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
idx = type + KM_TYPE_NR*smp_processor_id();
/*
@@ -252,6 +252,7 @@ void __kunmap_atomic(void *kvaddr)
BUG_ON(!pte_present(pteval) && !pte_migrating(pteval));
kmap_atomic_unregister(pte_page(pteval), vaddr);
kpte_clear_flush(pte, vaddr);
+ kmap_atomic_idx_pop();
} else {
/* Must be a lowmem page */
BUG_ON(vaddr < PAGE_OFFSET);
diff -puN arch/x86/mm/highmem_32.c~mm-fix-race-in-kunmap_atomic arch/x86/mm/highmem_32.c
--- a/arch/x86/mm/highmem_32.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/x86/mm/highmem_32.c
@@ -74,7 +74,7 @@ void __kunmap_atomic(void *kvaddr)
vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
int idx, type;
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
idx = type + KM_TYPE_NR * smp_processor_id();
#ifdef CONFIG_DEBUG_HIGHMEM
@@ -87,6 +87,7 @@ void __kunmap_atomic(void *kvaddr)
* attributes or becomes a protected page in a hypervisor.
*/
kpte_clear_flush(kmap_pte-idx, vaddr);
+ kmap_atomic_idx_pop();
}
#ifdef CONFIG_DEBUG_HIGHMEM
else {
diff -puN arch/x86/mm/iomap_32.c~mm-fix-race-in-kunmap_atomic arch/x86/mm/iomap_32.c
--- a/arch/x86/mm/iomap_32.c~mm-fix-race-in-kunmap_atomic
+++ a/arch/x86/mm/iomap_32.c
@@ -98,7 +98,7 @@ iounmap_atomic(void __iomem *kvaddr)
vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
int idx, type;
- type = kmap_atomic_idx_pop();
+ type = kmap_atomic_idx();
idx = type + KM_TYPE_NR * smp_processor_id();
#ifdef CONFIG_DEBUG_HIGHMEM
@@ -111,6 +111,7 @@ iounmap_atomic(void __iomem *kvaddr)
* attributes or becomes a protected page in a hypervisor.
*/
kpte_clear_flush(kmap_pte-idx, vaddr);
+ kmap_atomic_idx_pop();
}
pagefault_enable();
diff -puN include/linux/highmem.h~mm-fix-race-in-kunmap_atomic include/linux/highmem.h
--- a/include/linux/highmem.h~mm-fix-race-in-kunmap_atomic
+++ a/include/linux/highmem.h
@@ -88,6 +88,11 @@ static inline int kmap_atomic_idx_push(v
return idx;
}
+static inline int kmap_atomic_idx(void)
+{
+ return __get_cpu_var(__kmap_atomic_idx) - 1;
+}
+
static inline int kmap_atomic_idx_pop(void)
{
int idx = --__get_cpu_var(__kmap_atomic_idx);
_
Patches currently in -mm which might be from a.p.zijlstra@xxxxxxxxx are
origin.patch
writeback-remove-the-internal-5%-low-bound-on-dirty_ratio.patch
mm-strictly-nested-kmap_atomic.patch
mm-stack-based-kmap_atomic.patch
mm-remove-pte_map_nested.patch
perf-x86-fix-up-kmap_atomic-type.patch
mm-highmem-documentation.patch
mm-filemap_fault-unique-path-for-locking-page.patch
mm-retry-page-fault-when-blocking-on-disk-transfer.patch
x86-access_error-api-cleanup.patch
um-migrate-from-__do_irq-to-generic_handle_irq.patch
workqueues-s-on_stack-onstack.patch
kernel-remove-pf_flusher.patch
mmx86-fix-kmap_atomic_push-vs-ioremap_32c.patch
mm-fix-race-in-kunmap_atomic.patch
linux-next.patch
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