[linux-2.6-block.git] / mm / kmsan / core.c

// SPDX-License-Identifier: GPL-2.0
/*
 * KMSAN runtime library.
 *
 * Copyright (C) 2017-2022 Google LLC
 * Author: Alexander Potapenko <glider@google.com>
 *
 */

#include <asm/page.h>
#include <linux/compiler.h>
#include <linux/export.h>
#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/kmsan_types.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/mm_types.h>
#include <linux/mmzone.h>
#include <linux/percpu-defs.h>
#include <linux/preempt.h>
#include <linux/slab.h>
#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/types.h>
#include <linux/vmalloc.h>

#include "../slab.h"
#include "kmsan.h"

bool kmsan_enabled __read_mostly;

/*
 * Per-CPU KMSAN context to be used in interrupts, where current->kmsan is
 * unavaliable.
 */
DEFINE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);

void kmsan_internal_task_create(struct task_struct *task)
{
	struct kmsan_ctx *ctx = &task->kmsan_ctx;
	struct thread_info *info = current_thread_info();

	__memset(ctx, 0, sizeof(*ctx));
	ctx->allow_reporting = true;
	kmsan_internal_unpoison_memory(info, sizeof(*info), false);
}

void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,
				  unsigned int poison_flags)
{
	u32 extra_bits =
		kmsan_extra_bits(/*depth*/ 0, poison_flags & KMSAN_POISON_FREE);
	bool checked = poison_flags & KMSAN_POISON_CHECK;
	depot_stack_handle_t handle;

	handle = kmsan_save_stack_with_flags(flags, extra_bits);
	kmsan_internal_set_shadow_origin(address, size, -1, handle, checked);
}

void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked)
{
	kmsan_internal_set_shadow_origin(address, size, 0, 0, checked);
}

depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,
						 unsigned int extra)
{
	unsigned long entries[KMSAN_STACK_DEPTH];
	unsigned int nr_entries;

	nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0);

	/* Don't sleep (see might_sleep_if() in __alloc_pages_nodemask()). */
	flags &= ~__GFP_DIRECT_RECLAIM;

	return __stack_depot_save(entries, nr_entries, extra, flags, true);
}

/* Copy the metadata following the memmove() behavior. */
void kmsan_internal_memmove_metadata(void *dst, void *src, size_t n)
{
	depot_stack_handle_t old_origin = 0, new_origin = 0;
	int src_slots, dst_slots, i, iter, step, skip_bits;
	depot_stack_handle_t *origin_src, *origin_dst;
	void *shadow_src, *shadow_dst;
	u32 *align_shadow_src, shadow;
	bool backwards;

	shadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW);
	if (!shadow_dst)
		return;
	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n));

	shadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW);
	if (!shadow_src) {
		/*
		 * @src is untracked: zero out destination shadow, ignore the
		 * origins, we're done.
		 */
		__memset(shadow_dst, 0, n);
		return;
	}
	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n));

	__memmove(shadow_dst, shadow_src, n);

	origin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN);
	origin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN);
	KMSAN_WARN_ON(!origin_dst || !origin_src);
	src_slots = (ALIGN((u64)src + n, KMSAN_ORIGIN_SIZE) -
		     ALIGN_DOWN((u64)src, KMSAN_ORIGIN_SIZE)) /
		    KMSAN_ORIGIN_SIZE;
	dst_slots = (ALIGN((u64)dst + n, KMSAN_ORIGIN_SIZE) -
		     ALIGN_DOWN((u64)dst, KMSAN_ORIGIN_SIZE)) /
		    KMSAN_ORIGIN_SIZE;
	KMSAN_WARN_ON((src_slots < 1) || (dst_slots < 1));
	KMSAN_WARN_ON((src_slots - dst_slots > 1) ||
		      (dst_slots - src_slots < -1));

	backwards = dst > src;
	i = backwards ? min(src_slots, dst_slots) - 1 : 0;
	iter = backwards ? -1 : 1;

	align_shadow_src =
		(u32 *)ALIGN_DOWN((u64)shadow_src, KMSAN_ORIGIN_SIZE);
	for (step = 0; step < min(src_slots, dst_slots); step++, i += iter) {
		KMSAN_WARN_ON(i < 0);
		shadow = align_shadow_src[i];
		if (i == 0) {
			/*
			 * If @src isn't aligned on KMSAN_ORIGIN_SIZE, don't
			 * look at the first @src % KMSAN_ORIGIN_SIZE bytes
			 * of the first shadow slot.
			 */
			skip_bits = ((u64)src % KMSAN_ORIGIN_SIZE) * 8;
			shadow = (shadow >> skip_bits) << skip_bits;
		}
		if (i == src_slots - 1) {
			/*
			 * If @src + n isn't aligned on
			 * KMSAN_ORIGIN_SIZE, don't look at the last
			 * (@src + n) % KMSAN_ORIGIN_SIZE bytes of the
			 * last shadow slot.
			 */
			skip_bits = (((u64)src + n) % KMSAN_ORIGIN_SIZE) * 8;
			shadow = (shadow << skip_bits) >> skip_bits;
		}
		/*
		 * Overwrite the origin only if the corresponding
		 * shadow is nonempty.
		 */
		if (origin_src[i] && (origin_src[i] != old_origin) && shadow) {
			old_origin = origin_src[i];
			new_origin = kmsan_internal_chain_origin(old_origin);
			/*
			 * kmsan_internal_chain_origin() may return
			 * NULL, but we don't want to lose the previous
			 * origin value.
			 */
			if (!new_origin)
				new_origin = old_origin;
		}
		if (shadow)
			origin_dst[i] = new_origin;
		else
			origin_dst[i] = 0;
	}
	/*
	 * If dst_slots is greater than src_slots (i.e.
	 * dst_slots == src_slots + 1), there is an extra origin slot at the
	 * beginning or end of the destination buffer, for which we take the
	 * origin from the previous slot.
	 * This is only done if the part of the source shadow corresponding to
	 * slot is non-zero.
	 *
	 * E.g. if we copy 8 aligned bytes that are marked as uninitialized
	 * and have origins o111 and o222, to an unaligned buffer with offset 1,
	 * these two origins are copied to three origin slots, so one of then
	 * needs to be duplicated, depending on the copy direction (@backwards)
	 *
	 *   src shadow: |uuuu|uuuu|....|
	 *   src origin: |o111|o222|....|
	 *
	 * backwards = 0:
	 *   dst shadow: |.uuu|uuuu|u...|
	 *   dst origin: |....|o111|o222| - fill the empty slot with o111
	 * backwards = 1:
	 *   dst shadow: |.uuu|uuuu|u...|
	 *   dst origin: |o111|o222|....| - fill the empty slot with o222
	 */
	if (src_slots < dst_slots) {
		if (backwards) {
			shadow = align_shadow_src[src_slots - 1];
			skip_bits = (((u64)dst + n) % KMSAN_ORIGIN_SIZE) * 8;
			shadow = (shadow << skip_bits) >> skip_bits;
			if (shadow)
				/* src_slots > 0, therefore dst_slots is at least 2 */
				origin_dst[dst_slots - 1] =
					origin_dst[dst_slots - 2];
		} else {
			shadow = align_shadow_src[0];
			skip_bits = ((u64)dst % KMSAN_ORIGIN_SIZE) * 8;
			shadow = (shadow >> skip_bits) << skip_bits;
			if (shadow)
				origin_dst[0] = origin_dst[1];
		}
	}
}

depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id)
{
	unsigned long entries[3];
	u32 extra_bits;
	int depth;
	bool uaf;

	if (!id)
		return id;
	/*
	 * Make sure we have enough spare bits in @id to hold the UAF bit and
	 * the chain depth.
	 */
	BUILD_BUG_ON(
		(1 << STACK_DEPOT_EXTRA_BITS) <= (KMSAN_MAX_ORIGIN_DEPTH << 1));

	extra_bits = stack_depot_get_extra_bits(id);
	depth = kmsan_depth_from_eb(extra_bits);
	uaf = kmsan_uaf_from_eb(extra_bits);

	/*
	 * Stop chaining origins once the depth reached KMSAN_MAX_ORIGIN_DEPTH.
	 * This mostly happens in the case structures with uninitialized padding
	 * are copied around many times. Origin chains for such structures are
	 * usually periodic, and it does not make sense to fully store them.
	 */
	if (depth == KMSAN_MAX_ORIGIN_DEPTH)
		return id;

	depth++;
	extra_bits = kmsan_extra_bits(depth, uaf);

	entries[0] = KMSAN_CHAIN_MAGIC_ORIGIN;
	entries[1] = kmsan_save_stack_with_flags(GFP_ATOMIC, 0);
	entries[2] = id;
	/*
	 * @entries is a local var in non-instrumented code, so KMSAN does not
	 * know it is initialized. Explicitly unpoison it to avoid false
	 * positives when __stack_depot_save() passes it to instrumented code.
	 */
	kmsan_internal_unpoison_memory(entries, sizeof(entries), false);
	return __stack_depot_save(entries, ARRAY_SIZE(entries), extra_bits,
				  GFP_ATOMIC, true);
}

void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b,
				      u32 origin, bool checked)
{
	u64 address = (u64)addr;
	void *shadow_start;
	u32 *origin_start;
	size_t pad = 0;

	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size));
	shadow_start = kmsan_get_metadata(addr, KMSAN_META_SHADOW);
	if (!shadow_start) {
		/*
		 * kmsan_metadata_is_contiguous() is true, so either all shadow
		 * and origin pages are NULL, or all are non-NULL.
		 */
		if (checked) {
			pr_err("%s: not memsetting %ld bytes starting at %px, because the shadow is NULL\n",
			       __func__, size, addr);
			KMSAN_WARN_ON(true);
		}
		return;
	}
	__memset(shadow_start, b, size);

	if (!IS_ALIGNED(address, KMSAN_ORIGIN_SIZE)) {
		pad = address % KMSAN_ORIGIN_SIZE;
		address -= pad;
		size += pad;
	}
	size = ALIGN(size, KMSAN_ORIGIN_SIZE);
	origin_start =
		(u32 *)kmsan_get_metadata((void *)address, KMSAN_META_ORIGIN);

	for (int i = 0; i < size / KMSAN_ORIGIN_SIZE; i++)
		origin_start[i] = origin;
}

struct page *kmsan_vmalloc_to_page_or_null(void *vaddr)
{
	struct page *page;

	if (!kmsan_internal_is_vmalloc_addr(vaddr) &&
	    !kmsan_internal_is_module_addr(vaddr))
		return NULL;
	page = vmalloc_to_page(vaddr);
	if (pfn_valid(page_to_pfn(page)))
		return page;
	else
		return NULL;
}

void kmsan_internal_check_memory(void *addr, size_t size, const void *user_addr,
				 int reason)
{
	depot_stack_handle_t cur_origin = 0, new_origin = 0;
	unsigned long addr64 = (unsigned long)addr;
	depot_stack_handle_t *origin = NULL;
	unsigned char *shadow = NULL;
	int cur_off_start = -1;
	int chunk_size;
	size_t pos = 0;

	if (!size)
		return;
	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size));
	while (pos < size) {
		chunk_size = min(size - pos,
				 PAGE_SIZE - ((addr64 + pos) % PAGE_SIZE));
		shadow = kmsan_get_metadata((void *)(addr64 + pos),
					    KMSAN_META_SHADOW);
		if (!shadow) {
			/*
			 * This page is untracked. If there were uninitialized
			 * bytes before, report them.
			 */
			if (cur_origin) {
				kmsan_enter_runtime();
				kmsan_report(cur_origin, addr, size,
					     cur_off_start, pos - 1, user_addr,
					     reason);
				kmsan_leave_runtime();
			}
			cur_origin = 0;
			cur_off_start = -1;
			pos += chunk_size;
			continue;
		}
		for (int i = 0; i < chunk_size; i++) {
			if (!shadow[i]) {
				/*
				 * This byte is unpoisoned. If there were
				 * poisoned bytes before, report them.
				 */
				if (cur_origin) {
					kmsan_enter_runtime();
					kmsan_report(cur_origin, addr, size,
						     cur_off_start, pos + i - 1,
						     user_addr, reason);
					kmsan_leave_runtime();
				}
				cur_origin = 0;
				cur_off_start = -1;
				continue;
			}
			origin = kmsan_get_metadata((void *)(addr64 + pos + i),
						    KMSAN_META_ORIGIN);
			KMSAN_WARN_ON(!origin);
			new_origin = *origin;
			/*
			 * Encountered new origin - report the previous
			 * uninitialized range.
			 */
			if (cur_origin != new_origin) {
				if (cur_origin) {
					kmsan_enter_runtime();
					kmsan_report(cur_origin, addr, size,
						     cur_off_start, pos + i - 1,
						     user_addr, reason);
					kmsan_leave_runtime();
				}
				cur_origin = new_origin;
				cur_off_start = pos + i;
			}
		}
		pos += chunk_size;
	}
	KMSAN_WARN_ON(pos != size);
	if (cur_origin) {
		kmsan_enter_runtime();
		kmsan_report(cur_origin, addr, size, cur_off_start, pos - 1,
			     user_addr, reason);
		kmsan_leave_runtime();
	}
}

bool kmsan_metadata_is_contiguous(void *addr, size_t size)
{
	char *cur_shadow = NULL, *next_shadow = NULL, *cur_origin = NULL,
	     *next_origin = NULL;
	u64 cur_addr = (u64)addr, next_addr = cur_addr + PAGE_SIZE;
	depot_stack_handle_t *origin_p;
	bool all_untracked = false;

	if (!size)
		return true;

	/* The whole range belongs to the same page. */
	if (ALIGN_DOWN(cur_addr + size - 1, PAGE_SIZE) ==
	    ALIGN_DOWN(cur_addr, PAGE_SIZE))
		return true;

	cur_shadow = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ false);
	if (!cur_shadow)
		all_untracked = true;
	cur_origin = kmsan_get_metadata((void *)cur_addr, /*is_origin*/ true);
	if (all_untracked && cur_origin)
		goto report;

	for (; next_addr < (u64)addr + size;
	     cur_addr = next_addr, cur_shadow = next_shadow,
	     cur_origin = next_origin, next_addr += PAGE_SIZE) {
		next_shadow = kmsan_get_metadata((void *)next_addr, false);
		next_origin = kmsan_get_metadata((void *)next_addr, true);
		if (all_untracked) {
			if (next_shadow || next_origin)
				goto report;
			if (!next_shadow && !next_origin)
				continue;
		}
		if (((u64)cur_shadow == ((u64)next_shadow - PAGE_SIZE)) &&
		    ((u64)cur_origin == ((u64)next_origin - PAGE_SIZE)))
			continue;
		goto report;
	}
	return true;

report:
	pr_err("%s: attempting to access two shadow page ranges.\n", __func__);
	pr_err("Access of size %ld at %px.\n", size, addr);
	pr_err("Addresses belonging to different ranges: %px and %px\n",
	       (void *)cur_addr, (void *)next_addr);
	pr_err("page[0].shadow: %px, page[1].shadow: %px\n", cur_shadow,
	       next_shadow);
	pr_err("page[0].origin: %px, page[1].origin: %px\n", cur_origin,
	       next_origin);
	origin_p = kmsan_get_metadata(addr, KMSAN_META_ORIGIN);
	if (origin_p) {
		pr_err("Origin: %08x\n", *origin_p);
		kmsan_print_origin(*origin_p);
	} else {
		pr_err("Origin: unavailable\n");
	}
	return false;
}
Commit	Line	Data
f80be457 AP	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* KMSAN runtime library.
	4	*
	5	* Copyright (C) 2017-2022 Google LLC
	6	* Author: Alexander Potapenko <glider@google.com>
	7	*
	8	*/
	9
	10	#include <asm/page.h>
	11	#include <linux/compiler.h>
	12	#include <linux/export.h>
	13	#include <linux/highmem.h>
	14	#include <linux/interrupt.h>
	15	#include <linux/kernel.h>
	16	#include <linux/kmsan_types.h>
	17	#include <linux/memory.h>
	18	#include <linux/mm.h>
	19	#include <linux/mm_types.h>
	20	#include <linux/mmzone.h>
	21	#include <linux/percpu-defs.h>
	22	#include <linux/preempt.h>
	23	#include <linux/slab.h>
	24	#include <linux/stackdepot.h>
	25	#include <linux/stacktrace.h>
	26	#include <linux/types.h>
	27	#include <linux/vmalloc.h>
	28
	29	#include "../slab.h"
	30	#include "kmsan.h"
	31
	32	bool kmsan_enabled __read_mostly;
	33
	34	/*
	35	* Per-CPU KMSAN context to be used in interrupts, where current->kmsan is
	36	* unavaliable.
	37	*/
	38	DEFINE_PER_CPU(struct kmsan_ctx, kmsan_percpu_ctx);
	39
50b5e49c AP	40	void kmsan_internal_task_create(struct task_struct *task)
	41	{
	42	struct kmsan_ctx *ctx = &task->kmsan_ctx;
	43	struct thread_info *info = current_thread_info();
	44
	45	__memset(ctx, 0, sizeof(*ctx));
	46	ctx->allow_reporting = true;
	47	kmsan_internal_unpoison_memory(info, sizeof(*info), false);
	48	}
	49
f80be457 AP	50	void kmsan_internal_poison_memory(void *address, size_t size, gfp_t flags,
	51	unsigned int poison_flags)
	52	{
	53	u32 extra_bits =
	54	kmsan_extra_bits(/depth/ 0, poison_flags & KMSAN_POISON_FREE);
	55	bool checked = poison_flags & KMSAN_POISON_CHECK;
	56	depot_stack_handle_t handle;
	57
	58	handle = kmsan_save_stack_with_flags(flags, extra_bits);
	59	kmsan_internal_set_shadow_origin(address, size, -1, handle, checked);
	60	}
	61
	62	void kmsan_internal_unpoison_memory(void *address, size_t size, bool checked)
	63	{
	64	kmsan_internal_set_shadow_origin(address, size, 0, 0, checked);
	65	}
	66
	67	depot_stack_handle_t kmsan_save_stack_with_flags(gfp_t flags,
	68	unsigned int extra)
	69	{
	70	unsigned long entries[KMSAN_STACK_DEPTH];
	71	unsigned int nr_entries;
	72
	73	nr_entries = stack_trace_save(entries, KMSAN_STACK_DEPTH, 0);
	74
	75	/* Don't sleep (see might_sleep_if() in __alloc_pages_nodemask()). */
	76	flags &= ~__GFP_DIRECT_RECLAIM;
	77
	78	return __stack_depot_save(entries, nr_entries, extra, flags, true);
	79	}
	80
	81	/* Copy the metadata following the memmove() behavior. */
	82	void kmsan_internal_memmove_metadata(void dst, void src, size_t n)
	83	{
	84	depot_stack_handle_t old_origin = 0, new_origin = 0;
	85	int src_slots, dst_slots, i, iter, step, skip_bits;
	86	depot_stack_handle_t origin_src, origin_dst;
	87	void shadow_src, shadow_dst;
	88	u32 *align_shadow_src, shadow;
	89	bool backwards;
	90
	91	shadow_dst = kmsan_get_metadata(dst, KMSAN_META_SHADOW);
	92	if (!shadow_dst)
	93	return;
	94	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(dst, n));
	95
	96	shadow_src = kmsan_get_metadata(src, KMSAN_META_SHADOW);
	97	if (!shadow_src) {
	98	/*
	99	* @src is untracked: zero out destination shadow, ignore the
	100	* origins, we're done.
	101	*/
	102	__memset(shadow_dst, 0, n);
	103	return;
	104	}
	105	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(src, n));
	106
	107	__memmove(shadow_dst, shadow_src, n);
	108
	109	origin_dst = kmsan_get_metadata(dst, KMSAN_META_ORIGIN);
	110	origin_src = kmsan_get_metadata(src, KMSAN_META_ORIGIN);
	111	KMSAN_WARN_ON(!origin_dst \|\| !origin_src);
	112	src_slots = (ALIGN((u64)src + n, KMSAN_ORIGIN_SIZE) -
	113	ALIGN_DOWN((u64)src, KMSAN_ORIGIN_SIZE)) /
114	KMSAN_ORIGIN_SIZE;
115	dst_slots = (ALIGN((u64)dst + n, KMSAN_ORIGIN_SIZE) -
116	ALIGN_DOWN((u64)dst, KMSAN_ORIGIN_SIZE)) /
117	KMSAN_ORIGIN_SIZE;
118	KMSAN_WARN_ON((src_slots < 1) \|\| (dst_slots < 1));
119	KMSAN_WARN_ON((src_slots - dst_slots > 1) \|\|
120	(dst_slots - src_slots < -1));
121
122	backwards = dst > src;
123	i = backwards ? min(src_slots, dst_slots) - 1 : 0;
124	iter = backwards ? -1 : 1;
125
126	align_shadow_src =
127	(u32 *)ALIGN_DOWN((u64)shadow_src, KMSAN_ORIGIN_SIZE);
128	for (step = 0; step < min(src_slots, dst_slots); step++, i += iter) {
129	KMSAN_WARN_ON(i < 0);
130	shadow = align_shadow_src[i];
131	if (i == 0) {
132	/*
133	* If @src isn't aligned on KMSAN_ORIGIN_SIZE, don't
134	* look at the first @src % KMSAN_ORIGIN_SIZE bytes
135	* of the first shadow slot.
136	*/
137	skip_bits = ((u64)src % KMSAN_ORIGIN_SIZE) * 8;
138	shadow = (shadow >> skip_bits) << skip_bits;
139	}
140	if (i == src_slots - 1) {
141	/*
142	* If @src + n isn't aligned on
143	* KMSAN_ORIGIN_SIZE, don't look at the last
144	* (@src + n) % KMSAN_ORIGIN_SIZE bytes of the
145	* last shadow slot.
146	*/
147	skip_bits = (((u64)src + n) % KMSAN_ORIGIN_SIZE) * 8;
148	shadow = (shadow << skip_bits) >> skip_bits;
149	}
150	/*
151	* Overwrite the origin only if the corresponding
152	* shadow is nonempty.
153	*/
154	if (origin_src[i] && (origin_src[i] != old_origin) && shadow) {
155	old_origin = origin_src[i];
156	new_origin = kmsan_internal_chain_origin(old_origin);
157	/*
158	* kmsan_internal_chain_origin() may return
159	* NULL, but we don't want to lose the previous
160	* origin value.
161	*/
162	if (!new_origin)
163	new_origin = old_origin;
164	}
165	if (shadow)
166	origin_dst[i] = new_origin;
167	else
168	origin_dst[i] = 0;
169	}
170	/*
171	* If dst_slots is greater than src_slots (i.e.
172	* dst_slots == src_slots + 1), there is an extra origin slot at the
173	* beginning or end of the destination buffer, for which we take the
174	* origin from the previous slot.
175	* This is only done if the part of the source shadow corresponding to
176	* slot is non-zero.
177	*
178	* E.g. if we copy 8 aligned bytes that are marked as uninitialized
179	* and have origins o111 and o222, to an unaligned buffer with offset 1,
180	* these two origins are copied to three origin slots, so one of then
181	* needs to be duplicated, depending on the copy direction (@backwards)
182	*
183	* src shadow: \|uuuu\|uuuu\|....\|
184	* src origin: \|o111\|o222\|....\|
185	*
186	* backwards = 0:
187	* dst shadow: \|.uuu\|uuuu\|u...\|
188	* dst origin: \|....\|o111\|o222\| - fill the empty slot with o111
189	* backwards = 1:
190	* dst shadow: \|.uuu\|uuuu\|u...\|
191	* dst origin: \|o111\|o222\|....\| - fill the empty slot with o222
192	*/
193	if (src_slots < dst_slots) {
194	if (backwards) {
195	shadow = align_shadow_src[src_slots - 1];
196	skip_bits = (((u64)dst + n) % KMSAN_ORIGIN_SIZE) * 8;
197	shadow = (shadow << skip_bits) >> skip_bits;
198	if (shadow)
199	/* src_slots > 0, therefore dst_slots is at least 2 */
200	origin_dst[dst_slots - 1] =
201	origin_dst[dst_slots - 2];
202	} else {
203	shadow = align_shadow_src[0];
204	skip_bits = ((u64)dst % KMSAN_ORIGIN_SIZE) * 8;
205	shadow = (shadow >> skip_bits) << skip_bits;
206	if (shadow)
207	origin_dst[0] = origin_dst[1];
208	}
209	}
210	}
211
212	depot_stack_handle_t kmsan_internal_chain_origin(depot_stack_handle_t id)
213	{
214	unsigned long entries[3];
215	u32 extra_bits;
216	int depth;
217	bool uaf;
218
219	if (!id)
220	return id;
221	/*
222	* Make sure we have enough spare bits in @id to hold the UAF bit and
223	* the chain depth.
224	*/
225	BUILD_BUG_ON(
226	(1 << STACK_DEPOT_EXTRA_BITS) <= (KMSAN_MAX_ORIGIN_DEPTH << 1));
227
228	extra_bits = stack_depot_get_extra_bits(id);
229	depth = kmsan_depth_from_eb(extra_bits);
230	uaf = kmsan_uaf_from_eb(extra_bits);
231
232	/*
233	* Stop chaining origins once the depth reached KMSAN_MAX_ORIGIN_DEPTH.
234	* This mostly happens in the case structures with uninitialized padding
235	* are copied around many times. Origin chains for such structures are
236	* usually periodic, and it does not make sense to fully store them.
237	*/
238	if (depth == KMSAN_MAX_ORIGIN_DEPTH)
239	return id;
240
241	depth++;
242	extra_bits = kmsan_extra_bits(depth, uaf);
243
244	entries[0] = KMSAN_CHAIN_MAGIC_ORIGIN;
245	entries[1] = kmsan_save_stack_with_flags(GFP_ATOMIC, 0);
246	entries[2] = id;
247	/*
248	* @entries is a local var in non-instrumented code, so KMSAN does not
249	* know it is initialized. Explicitly unpoison it to avoid false
250	* positives when __stack_depot_save() passes it to instrumented code.
251	*/
252	kmsan_internal_unpoison_memory(entries, sizeof(entries), false);
253	return __stack_depot_save(entries, ARRAY_SIZE(entries), extra_bits,
254	GFP_ATOMIC, true);
255	}
256
257	void kmsan_internal_set_shadow_origin(void *addr, size_t size, int b,
258	u32 origin, bool checked)
259	{
260	u64 address = (u64)addr;
261	void *shadow_start;
262	u32 *origin_start;
263	size_t pad = 0;
264
265	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size));
266	shadow_start = kmsan_get_metadata(addr, KMSAN_META_SHADOW);
267	if (!shadow_start) {
268	/*
269	* kmsan_metadata_is_contiguous() is true, so either all shadow
270	* and origin pages are NULL, or all are non-NULL.
271	*/
272	if (checked) {
273	pr_err("%s: not memsetting %ld bytes starting at %px, because the shadow is NULL\n",
274	__func__, size, addr);
275	KMSAN_WARN_ON(true);
276	}
277	return;
278	}
279	__memset(shadow_start, b, size);
280
281	if (!IS_ALIGNED(address, KMSAN_ORIGIN_SIZE)) {
282	pad = address % KMSAN_ORIGIN_SIZE;
283	address -= pad;
284	size += pad;
285	}
286	size = ALIGN(size, KMSAN_ORIGIN_SIZE);
287	origin_start =
288	(u32 )kmsan_get_metadata((void )address, KMSAN_META_ORIGIN);
289
290	for (int i = 0; i < size / KMSAN_ORIGIN_SIZE; i++)
291	origin_start[i] = origin;
292	}
293
294	struct page kmsan_vmalloc_to_page_or_null(void vaddr)
295	{
296	struct page *page;
297
298	if (!kmsan_internal_is_vmalloc_addr(vaddr) &&
299	!kmsan_internal_is_module_addr(vaddr))
300	return NULL;
301	page = vmalloc_to_page(vaddr);
302	if (pfn_valid(page_to_pfn(page)))
303	return page;
304	else
305	return NULL;
306	}
307
308	void kmsan_internal_check_memory(void addr, size_t size, const void user_addr,
309	int reason)
310	{
311	depot_stack_handle_t cur_origin = 0, new_origin = 0;
312	unsigned long addr64 = (unsigned long)addr;
313	depot_stack_handle_t *origin = NULL;
314	unsigned char *shadow = NULL;
315	int cur_off_start = -1;
316	int chunk_size;
317	size_t pos = 0;
318
319	if (!size)
320	return;
321	KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(addr, size));
322	while (pos < size) {
323	chunk_size = min(size - pos,
324	PAGE_SIZE - ((addr64 + pos) % PAGE_SIZE));
325	shadow = kmsan_get_metadata((void *)(addr64 + pos),
326	KMSAN_META_SHADOW);
327	if (!shadow) {
328	/*
329	* This page is untracked. If there were uninitialized
330	* bytes before, report them.
331	*/
332	if (cur_origin) {
333	kmsan_enter_runtime();
334	kmsan_report(cur_origin, addr, size,
335	cur_off_start, pos - 1, user_addr,
336	reason);
337	kmsan_leave_runtime();
338	}
339	cur_origin = 0;
340	cur_off_start = -1;
341	pos += chunk_size;
342	continue;
343	}
344	for (int i = 0; i < chunk_size; i++) {
345	if (!shadow[i]) {
346	/*
347	* This byte is unpoisoned. If there were
348	* poisoned bytes before, report them.
349	*/
350	if (cur_origin) {
351	kmsan_enter_runtime();
352	kmsan_report(cur_origin, addr, size,
353	cur_off_start, pos + i - 1,
354	user_addr, reason);
355	kmsan_leave_runtime();
356	}
357	cur_origin = 0;
358	cur_off_start = -1;
359	continue;
360	}
361	origin = kmsan_get_metadata((void *)(addr64 + pos + i),
362	KMSAN_META_ORIGIN);
363	KMSAN_WARN_ON(!origin);
364	new_origin = *origin;
365	/*
366	* Encountered new origin - report the previous
367	* uninitialized range.
368	*/
369	if (cur_origin != new_origin) {
370	if (cur_origin) {
371	kmsan_enter_runtime();
372	kmsan_report(cur_origin, addr, size,
373	cur_off_start, pos + i - 1,
374	user_addr, reason);
375	kmsan_leave_runtime();
376	}
377	cur_origin = new_origin;
378	cur_off_start = pos + i;
379	}
380	}
381	pos += chunk_size;
382	}
383	KMSAN_WARN_ON(pos != size);
384	if (cur_origin) {
385	kmsan_enter_runtime();
386	kmsan_report(cur_origin, addr, size, cur_off_start, pos - 1,
387	user_addr, reason);
388	kmsan_leave_runtime();
389	}
390	}
391
392	bool kmsan_metadata_is_contiguous(void *addr, size_t size)
393	{
394	char cur_shadow = NULL, next_shadow = NULL, *cur_origin = NULL,
395	*next_origin = NULL;
396	u64 cur_addr = (u64)addr, next_addr = cur_addr + PAGE_SIZE;
397	depot_stack_handle_t *origin_p;
398	bool all_untracked = false;
399
400	if (!size)
401	return true;
402
403	/* The whole range belongs to the same page. */
404	if (ALIGN_DOWN(cur_addr + size - 1, PAGE_SIZE) ==
405	ALIGN_DOWN(cur_addr, PAGE_SIZE))
406	return true;
407
408	cur_shadow = kmsan_get_metadata((void )cur_addr, /is_origin*/ false);
409	if (!cur_shadow)
410	all_untracked = true;
411	cur_origin = kmsan_get_metadata((void )cur_addr, /is_origin*/ true);
412	if (all_untracked && cur_origin)
413	goto report;
414
415	for (; next_addr < (u64)addr + size;
416	cur_addr = next_addr, cur_shadow = next_shadow,
417	cur_origin = next_origin, next_addr += PAGE_SIZE) {
418	next_shadow = kmsan_get_metadata((void *)next_addr, false);
419	next_origin = kmsan_get_metadata((void *)next_addr, true);
420	if (all_untracked) {
421	if (next_shadow \|\| next_origin)
422	goto report;
423	if (!next_shadow && !next_origin)
424	continue;
425	}
426	if (((u64)cur_shadow == ((u64)next_shadow - PAGE_SIZE)) &&
427	((u64)cur_origin == ((u64)next_origin - PAGE_SIZE)))
428	continue;
429	goto report;
430	}
431	return true;
432
433	report:
434	pr_err("%s: attempting to access two shadow page ranges.\n", __func__);
435	pr_err("Access of size %ld at %px.\n", size, addr);
436	pr_err("Addresses belonging to different ranges: %px and %px\n",
437	(void )cur_addr, (void )next_addr);
438	pr_err("page[0].shadow: %px, page[1].shadow: %px\n", cur_shadow,
439	next_shadow);
440	pr_err("page[0].origin: %px, page[1].origin: %px\n", cur_origin,
441	next_origin);
442	origin_p = kmsan_get_metadata(addr, KMSAN_META_ORIGIN);
443	if (origin_p) {
444	pr_err("Origin: %08x\n", *origin_p);
445	kmsan_print_origin(*origin_p);
446	} else {
447	pr_err("Origin: unavailable\n");
448	}
449	return false;
450	}