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