From 20273941f2129aa5a432796d98a276ed73d60782 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 27 Oct 2010 15:32:58 -0700 Subject: mm: fix race in kunmap_atomic() 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 Reported-by: Christoph Hellwig Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c index c00f119..c435fd9 100644 --- a/arch/arm/mm/highmem.c +++ b/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 --git a/arch/frv/mm/highmem.c b/arch/frv/mm/highmem.c index 61088dc..fd7fcd4 100644 --- a/arch/frv/mm/highmem.c +++ b/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 --git a/arch/mips/mm/highmem.c b/arch/mips/mm/highmem.c index 1e69b1f..3634c7ea 100644 --- a/arch/mips/mm/highmem.c +++ b/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 --git a/arch/mn10300/include/asm/highmem.h b/arch/mn10300/include/asm/highmem.h index f577ba2..e2155e6 100644 --- a/arch/mn10300/include/asm/highmem.h +++ b/arch/mn10300/include/asm/highmem.h @@ -101,7 +101,7 @@ static inline void __kunmap_atomic(unsigned long vaddr) return; } - type = kmap_atomic_idx_pop(); + type = kmap_atomic_idx(); #if HIGHMEM_DEBUG { @@ -119,6 +119,8 @@ static inline void __kunmap_atomic(unsigned long vaddr) __flush_tlb_one(vaddr); } #endif + + kmap_atomic_idx_pop(); pagefault_enable(); } #endif /* __KERNEL__ */ diff --git a/arch/powerpc/mm/highmem.c b/arch/powerpc/mm/highmem.c index b0848b4..e7450bd 100644 --- a/arch/powerpc/mm/highmem.c +++ b/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 --git a/arch/sparc/mm/highmem.c b/arch/sparc/mm/highmem.c index 5e50c09..4730eac 100644 --- a/arch/sparc/mm/highmem.c +++ b/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 --git a/arch/tile/mm/highmem.c b/arch/tile/mm/highmem.c index 8ef6595..abb5733 100644 --- a/arch/tile/mm/highmem.c +++ b/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 --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c index d723e36..b499626 100644 --- a/arch/x86/mm/highmem_32.c +++ b/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 --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c index 75a3d7f..7b179b49 100644 --- a/arch/x86/mm/iomap_32.c +++ b/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 --git a/include/linux/highmem.h b/include/linux/highmem.h index 102f76b..e913819 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -88,6 +88,11 @@ static inline int kmap_atomic_idx_push(void) 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); -- cgit v1.1