212 lines
6.9 KiB
C
212 lines
6.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Functions used by the KMSAN runtime.
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*
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* Copyright (C) 2017-2022 Google LLC
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* Author: Alexander Potapenko <glider@google.com>
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*
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*/
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#ifndef __MM_KMSAN_KMSAN_H
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#define __MM_KMSAN_KMSAN_H
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#include <asm/pgtable_64_types.h>
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#include <linux/irqflags.h>
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#include <linux/sched.h>
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#include <linux/stackdepot.h>
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#include <linux/stacktrace.h>
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#include <linux/nmi.h>
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#include <linux/mm.h>
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#include <linux/printk.h>
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#define KMSAN_ALLOCA_MAGIC_ORIGIN 0xabcd0100
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#define KMSAN_CHAIN_MAGIC_ORIGIN 0xabcd0200
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#define KMSAN_POISON_NOCHECK 0x0
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#define KMSAN_POISON_CHECK 0x1
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#define KMSAN_POISON_FREE 0x2
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#define KMSAN_ORIGIN_SIZE 4
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#define KMSAN_MAX_ORIGIN_DEPTH 7
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#define KMSAN_STACK_DEPTH 64
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#define KMSAN_META_SHADOW (false)
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#define KMSAN_META_ORIGIN (true)
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extern bool kmsan_enabled;
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extern int panic_on_kmsan;
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/*
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* KMSAN performs a lot of consistency checks that are currently enabled by
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* default. BUG_ON is normally discouraged in the kernel, unless used for
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* debugging, but KMSAN itself is a debugging tool, so it makes little sense to
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* recover if something goes wrong.
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*/
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#define KMSAN_WARN_ON(cond) \
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({ \
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const bool __cond = WARN_ON(cond); \
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if (unlikely(__cond)) { \
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WRITE_ONCE(kmsan_enabled, false); \
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if (panic_on_kmsan) { \
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/* Can't call panic() here because */ \
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/* of uaccess checks. */ \
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BUG(); \
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} \
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} \
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__cond; \
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})
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/*
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* A pair of metadata pointers to be returned by the instrumentation functions.
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*/
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struct shadow_origin_ptr {
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void *shadow, *origin;
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};
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struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *addr, u64 size,
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bool store);
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void *kmsan_get_metadata(void *addr, bool is_origin);
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void __init kmsan_init_alloc_meta_for_range(void *start, void *end);
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enum kmsan_bug_reason {
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REASON_ANY,
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REASON_COPY_TO_USER,
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REASON_SUBMIT_URB,
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};
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void kmsan_print_origin(depot_stack_handle_t origin);
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/**
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* kmsan_report() - Report a use of uninitialized value.
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* @origin: Stack ID of the uninitialized value.
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* @address: Address at which the memory access happens.
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* @size: Memory access size.
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* @off_first: Offset (from @address) of the first byte to be reported.
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* @off_last: Offset (from @address) of the last byte to be reported.
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* @user_addr: When non-NULL, denotes the userspace address to which the kernel
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* is leaking data.
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* @reason: Error type from enum kmsan_bug_reason.
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*
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* kmsan_report() prints an error message for a consequent group of bytes
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* sharing the same origin. If an uninitialized value is used in a comparison,
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* this function is called once without specifying the addresses. When checking
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* a memory range, KMSAN may call kmsan_report() multiple times with the same
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* @address, @size, @user_addr and @reason, but different @off_first and
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* @off_last corresponding to different @origin values.
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*/
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void kmsan_report(depot_stack_handle_t origin, void *address, int size,
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int off_first, int off_last, const void *user_addr,
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enum kmsan_bug_reason reason);
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DECLARE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);
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static __always_inline struct kmsan_ctx *kmsan_get_context(void)
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{
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return in_task() ? ¤t->kmsan_ctx : raw_cpu_ptr(&kmsan_percpu_ctx);
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}
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/*
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* When a compiler hook or KMSAN runtime function is invoked, it may make a
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* call to instrumented code and eventually call itself recursively. To avoid
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* that, we guard the runtime entry regions with
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* kmsan_enter_runtime()/kmsan_leave_runtime() and exit the hook if
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* kmsan_in_runtime() is true.
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*
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* Non-runtime code may occasionally get executed in nested IRQs from the
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* runtime code (e.g. when called via smp_call_function_single()). Because some
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* KMSAN routines may take locks (e.g. for memory allocation), we conservatively
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* bail out instead of calling them. To minimize the effect of this (potentially
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* missing initialization events) kmsan_in_runtime() is not checked in
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* non-blocking runtime functions.
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*/
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static __always_inline bool kmsan_in_runtime(void)
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{
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if ((hardirq_count() >> HARDIRQ_SHIFT) > 1)
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return true;
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if (in_nmi())
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return true;
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return kmsan_get_context()->kmsan_in_runtime;
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}
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static __always_inline void kmsan_enter_runtime(void)
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{
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struct kmsan_ctx *ctx;
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ctx = kmsan_get_context();
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KMSAN_WARN_ON(ctx->kmsan_in_runtime++);
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}
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static __always_inline void kmsan_leave_runtime(void)
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{
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struct kmsan_ctx *ctx = kmsan_get_context();
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KMSAN_WARN_ON(--ctx->kmsan_in_runtime);
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}
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depot_stack_handle_t kmsan_save_stack(void);
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depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,
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unsigned int extra_bits);
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/*
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* Pack and unpack the origin chain depth and UAF flag to/from the extra bits
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* provided by the stack depot.
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* The UAF flag is stored in the lowest bit, followed by the depth in the upper
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* bits.
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* set_dsh_extra_bits() is responsible for clamping the value.
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*/
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static __always_inline unsigned int kmsan_extra_bits(unsigned int depth,
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bool uaf)
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{
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return (depth << 1) | uaf;
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}
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static __always_inline bool kmsan_uaf_from_eb(unsigned int extra_bits)
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{
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return extra_bits & 1;
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}
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static __always_inline unsigned int kmsan_depth_from_eb(unsigned int extra_bits)
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{
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return extra_bits >> 1;
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}
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/*
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* kmsan_internal_ functions are supposed to be very simple and not require the
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* kmsan_in_runtime() checks.
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*/
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void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n);
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void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,
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unsigned int poison_flags);
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void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked);
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void kmsan_internal_set_shadow_origin(void *address, size_t size, int b,
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u32 origin, bool checked);
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depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id);
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void kmsan_internal_task_create(struct task_struct *task);
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bool kmsan_metadata_is_contiguous(void *addr, size_t size);
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void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr,
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int reason);
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struct page *kmsan_vmalloc_to_page_or_null(void *vaddr);
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void kmsan_setup_meta(struct page *page, struct page *shadow,
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struct page *origin, int order);
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/*
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* kmsan_internal_is_module_addr() and kmsan_internal_is_vmalloc_addr() are
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* non-instrumented versions of is_module_address() and is_vmalloc_addr() that
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* are safe to call from KMSAN runtime without recursion.
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*/
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static inline bool kmsan_internal_is_module_addr(void *vaddr)
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{
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return ((u64)vaddr >= MODULES_VADDR) && ((u64)vaddr < MODULES_END);
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}
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static inline bool kmsan_internal_is_vmalloc_addr(void *addr)
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{
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return ((u64)addr >= VMALLOC_START) && ((u64)addr < VMALLOC_END);
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}
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#endif /* __MM_KMSAN_KMSAN_H */
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