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e3ae116339
Functions which the compiler has instrumented for ASAN place poison on the stack shadow upon entry and remove this poison prior to returning. In some cases (e.g. hotplug and idle), CPUs may exit the kernel a number of levels deep in C code. If there are any instrumented functions on this critical path, these will leave portions of the idle thread stack shadow poisoned. If a CPU returns to the kernel via a different path (e.g. a cold entry), then depending on stack frame layout subsequent calls to instrumented functions may use regions of the stack with stale poison, resulting in (spurious) KASAN splats to the console. Contemporary GCCs always add stack shadow poisoning when ASAN is enabled, even when asked to not instrument a function [1], so we can't simply annotate functions on the critical path to avoid poisoning. Instead, this series explicitly removes any stale poison before it can be hit. In the common hotplug case we clear the entire stack shadow in common code, before a CPU is brought online. On architectures which perform a cold return as part of cpu idle may retain an architecture-specific amount of stack contents. To retain the poison for this retained context, the arch code must call the core KASAN code, passing a "watermark" stack pointer value beyond which shadow will be cleared. Architectures which don't perform a cold return as part of idle do not need any additional code. This patch (of 3): Functions which the compiler has instrumented for KASAN place poison on the stack shadow upon entry and remove this poision prior to returning. In some cases (e.g. hotplug and idle), CPUs may exit the kernel a number of levels deep in C code. If there are any instrumented functions on this critical path, these will leave portions of the stack shadow poisoned. If a CPU returns to the kernel via a different path (e.g. a cold entry), then depending on stack frame layout subsequent calls to instrumented functions may use regions of the stack with stale poison, resulting in (spurious) KASAN splats to the console. To avoid this, we must clear stale poison from the stack prior to instrumented functions being called. This patch adds functions to the KASAN core for removing poison from (portions of) a task's stack. These will be used by subsequent patches to avoid problems with hotplug and idle. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
101 lines
3.1 KiB
C
101 lines
3.1 KiB
C
#ifndef _LINUX_KASAN_H
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#define _LINUX_KASAN_H
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#include <linux/sched.h>
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#include <linux/types.h>
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struct kmem_cache;
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struct page;
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struct vm_struct;
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#ifdef CONFIG_KASAN
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#define KASAN_SHADOW_SCALE_SHIFT 3
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#include <asm/kasan.h>
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#include <asm/pgtable.h>
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extern unsigned char kasan_zero_page[PAGE_SIZE];
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extern pte_t kasan_zero_pte[PTRS_PER_PTE];
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extern pmd_t kasan_zero_pmd[PTRS_PER_PMD];
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extern pud_t kasan_zero_pud[PTRS_PER_PUD];
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void kasan_populate_zero_shadow(const void *shadow_start,
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const void *shadow_end);
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static inline void *kasan_mem_to_shadow(const void *addr)
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{
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return (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT)
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+ KASAN_SHADOW_OFFSET;
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}
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/* Enable reporting bugs after kasan_disable_current() */
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static inline void kasan_enable_current(void)
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{
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current->kasan_depth++;
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}
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/* Disable reporting bugs for current task */
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static inline void kasan_disable_current(void)
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{
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current->kasan_depth--;
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}
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void kasan_unpoison_shadow(const void *address, size_t size);
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void kasan_unpoison_task_stack(struct task_struct *task);
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void kasan_alloc_pages(struct page *page, unsigned int order);
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void kasan_free_pages(struct page *page, unsigned int order);
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void kasan_poison_slab(struct page *page);
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void kasan_unpoison_object_data(struct kmem_cache *cache, void *object);
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void kasan_poison_object_data(struct kmem_cache *cache, void *object);
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void kasan_kmalloc_large(const void *ptr, size_t size);
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void kasan_kfree_large(const void *ptr);
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void kasan_kfree(void *ptr);
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void kasan_kmalloc(struct kmem_cache *s, const void *object, size_t size);
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void kasan_krealloc(const void *object, size_t new_size);
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void kasan_slab_alloc(struct kmem_cache *s, void *object);
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void kasan_slab_free(struct kmem_cache *s, void *object);
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int kasan_module_alloc(void *addr, size_t size);
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void kasan_free_shadow(const struct vm_struct *vm);
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#else /* CONFIG_KASAN */
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static inline void kasan_unpoison_shadow(const void *address, size_t size) {}
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static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
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static inline void kasan_enable_current(void) {}
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static inline void kasan_disable_current(void) {}
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static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
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static inline void kasan_free_pages(struct page *page, unsigned int order) {}
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static inline void kasan_poison_slab(struct page *page) {}
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static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
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void *object) {}
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static inline void kasan_poison_object_data(struct kmem_cache *cache,
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void *object) {}
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static inline void kasan_kmalloc_large(void *ptr, size_t size) {}
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static inline void kasan_kfree_large(const void *ptr) {}
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static inline void kasan_kfree(void *ptr) {}
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static inline void kasan_kmalloc(struct kmem_cache *s, const void *object,
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size_t size) {}
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static inline void kasan_krealloc(const void *object, size_t new_size) {}
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static inline void kasan_slab_alloc(struct kmem_cache *s, void *object) {}
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static inline void kasan_slab_free(struct kmem_cache *s, void *object) {}
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static inline int kasan_module_alloc(void *addr, size_t size) { return 0; }
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static inline void kasan_free_shadow(const struct vm_struct *vm) {}
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#endif /* CONFIG_KASAN */
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#endif /* LINUX_KASAN_H */
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