| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * KASAN quarantine. |
| * |
| * Author: Alexander Potapenko <glider@google.com> |
| * Copyright (C) 2016 Google, Inc. |
| * |
| * Based on code by Dmitry Chernenkov. |
| */ |
| |
| #include <linux/gfp.h> |
| #include <linux/hash.h> |
| #include <linux/kernel.h> |
| #include <linux/mm.h> |
| #include <linux/percpu.h> |
| #include <linux/printk.h> |
| #include <linux/shrinker.h> |
| #include <linux/slab.h> |
| #include <linux/srcu.h> |
| #include <linux/string.h> |
| #include <linux/types.h> |
| #include <linux/cpuhotplug.h> |
| |
| #include "../slab.h" |
| #include "kasan.h" |
| |
| /* Data structure and operations for quarantine queues. */ |
| |
| /* |
| * Each queue is a signle-linked list, which also stores the total size of |
| * objects inside of it. |
| */ |
| struct qlist_head { |
| struct qlist_node *head; |
| struct qlist_node *tail; |
| size_t bytes; |
| bool offline; |
| }; |
| |
| #define QLIST_INIT { NULL, NULL, 0 } |
| |
| static bool qlist_empty(struct qlist_head *q) |
| { |
| return !q->head; |
| } |
| |
| static void qlist_init(struct qlist_head *q) |
| { |
| q->head = q->tail = NULL; |
| q->bytes = 0; |
| } |
| |
| static void qlist_put(struct qlist_head *q, struct qlist_node *qlink, |
| size_t size) |
| { |
| if (unlikely(qlist_empty(q))) |
| q->head = qlink; |
| else |
| q->tail->next = qlink; |
| q->tail = qlink; |
| qlink->next = NULL; |
| q->bytes += size; |
| } |
| |
| static void qlist_move_all(struct qlist_head *from, struct qlist_head *to) |
| { |
| if (unlikely(qlist_empty(from))) |
| return; |
| |
| if (qlist_empty(to)) { |
| *to = *from; |
| qlist_init(from); |
| return; |
| } |
| |
| to->tail->next = from->head; |
| to->tail = from->tail; |
| to->bytes += from->bytes; |
| |
| qlist_init(from); |
| } |
| |
| #define QUARANTINE_PERCPU_SIZE (1 << 20) |
| #define QUARANTINE_BATCHES \ |
| (1024 > 4 * CONFIG_NR_CPUS ? 1024 : 4 * CONFIG_NR_CPUS) |
| |
| /* |
| * The object quarantine consists of per-cpu queues and a global queue, |
| * guarded by quarantine_lock. |
| */ |
| static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine); |
| |
| /* Round-robin FIFO array of batches. */ |
| static struct qlist_head global_quarantine[QUARANTINE_BATCHES]; |
| static int quarantine_head; |
| static int quarantine_tail; |
| /* Total size of all objects in global_quarantine across all batches. */ |
| static unsigned long quarantine_size; |
| static DEFINE_RAW_SPINLOCK(quarantine_lock); |
| DEFINE_STATIC_SRCU(remove_cache_srcu); |
| |
| /* Maximum size of the global queue. */ |
| static unsigned long quarantine_max_size; |
| |
| /* |
| * Target size of a batch in global_quarantine. |
| * Usually equal to QUARANTINE_PERCPU_SIZE unless we have too much RAM. |
| */ |
| static unsigned long quarantine_batch_size; |
| |
| /* |
| * The fraction of physical memory the quarantine is allowed to occupy. |
| * Quarantine doesn't support memory shrinker with SLAB allocator, so we keep |
| * the ratio low to avoid OOM. |
| */ |
| #define QUARANTINE_FRACTION 32 |
| |
| static struct kmem_cache *qlink_to_cache(struct qlist_node *qlink) |
| { |
| return virt_to_head_page(qlink)->slab_cache; |
| } |
| |
| static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) |
| { |
| struct kasan_free_meta *free_info = |
| container_of(qlink, struct kasan_free_meta, |
| quarantine_link); |
| |
| return ((void *)free_info) - cache->kasan_info.free_meta_offset; |
| } |
| |
| static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) |
| { |
| void *object = qlink_to_object(qlink, cache); |
| struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); |
| unsigned long flags; |
| |
| if (IS_ENABLED(CONFIG_SLAB)) |
| local_irq_save(flags); |
| |
| /* |
| * If init_on_free is enabled and KASAN's free metadata is stored in |
| * the object, zero the metadata. Otherwise, the object's memory will |
| * not be properly zeroed, as KASAN saves the metadata after the slab |
| * allocator zeroes the object. |
| */ |
| if (slab_want_init_on_free(cache) && |
| cache->kasan_info.free_meta_offset == 0) |
| memzero_explicit(meta, sizeof(*meta)); |
| |
| /* |
| * As the object now gets freed from the quaratine, assume that its |
| * free track is no longer valid. |
| */ |
| *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREE; |
| |
| ___cache_free(cache, object, _THIS_IP_); |
| |
| if (IS_ENABLED(CONFIG_SLAB)) |
| local_irq_restore(flags); |
| } |
| |
| static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache) |
| { |
| struct qlist_node *qlink; |
| |
| if (unlikely(qlist_empty(q))) |
| return; |
| |
| qlink = q->head; |
| while (qlink) { |
| struct kmem_cache *obj_cache = |
| cache ? cache : qlink_to_cache(qlink); |
| struct qlist_node *next = qlink->next; |
| |
| qlink_free(qlink, obj_cache); |
| qlink = next; |
| } |
| qlist_init(q); |
| } |
| |
| bool kasan_quarantine_put(struct kmem_cache *cache, void *object) |
| { |
| unsigned long flags; |
| struct qlist_head *q; |
| struct qlist_head temp = QLIST_INIT; |
| struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); |
| |
| /* |
| * If there's no metadata for this object, don't put it into |
| * quarantine. |
| */ |
| if (!meta) |
| return false; |
| |
| /* |
| * Note: irq must be disabled until after we move the batch to the |
| * global quarantine. Otherwise kasan_quarantine_remove_cache() can |
| * miss some objects belonging to the cache if they are in our local |
| * temp list. kasan_quarantine_remove_cache() executes on_each_cpu() |
| * at the beginning which ensures that it either sees the objects in |
| * per-cpu lists or in the global quarantine. |
| */ |
| local_irq_save(flags); |
| |
| q = this_cpu_ptr(&cpu_quarantine); |
| if (q->offline) { |
| local_irq_restore(flags); |
| return false; |
| } |
| qlist_put(q, &meta->quarantine_link, cache->size); |
| if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) { |
| qlist_move_all(q, &temp); |
| |
| raw_spin_lock(&quarantine_lock); |
| WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes); |
| qlist_move_all(&temp, &global_quarantine[quarantine_tail]); |
| if (global_quarantine[quarantine_tail].bytes >= |
| READ_ONCE(quarantine_batch_size)) { |
| int new_tail; |
| |
| new_tail = quarantine_tail + 1; |
| if (new_tail == QUARANTINE_BATCHES) |
| new_tail = 0; |
| if (new_tail != quarantine_head) |
| quarantine_tail = new_tail; |
| } |
| raw_spin_unlock(&quarantine_lock); |
| } |
| |
| local_irq_restore(flags); |
| |
| return true; |
| } |
| |
| void kasan_quarantine_reduce(void) |
| { |
| size_t total_size, new_quarantine_size, percpu_quarantines; |
| unsigned long flags; |
| int srcu_idx; |
| struct qlist_head to_free = QLIST_INIT; |
| |
| if (likely(READ_ONCE(quarantine_size) <= |
| READ_ONCE(quarantine_max_size))) |
| return; |
| |
| /* |
| * srcu critical section ensures that kasan_quarantine_remove_cache() |
| * will not miss objects belonging to the cache while they are in our |
| * local to_free list. srcu is chosen because (1) it gives us private |
| * grace period domain that does not interfere with anything else, |
| * and (2) it allows synchronize_srcu() to return without waiting |
| * if there are no pending read critical sections (which is the |
| * expected case). |
| */ |
| srcu_idx = srcu_read_lock(&remove_cache_srcu); |
| raw_spin_lock_irqsave(&quarantine_lock, flags); |
| |
| /* |
| * Update quarantine size in case of hotplug. Allocate a fraction of |
| * the installed memory to quarantine minus per-cpu queue limits. |
| */ |
| total_size = (totalram_pages() << PAGE_SHIFT) / |
| QUARANTINE_FRACTION; |
| percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus(); |
| new_quarantine_size = (total_size < percpu_quarantines) ? |
| 0 : total_size - percpu_quarantines; |
| WRITE_ONCE(quarantine_max_size, new_quarantine_size); |
| /* Aim at consuming at most 1/2 of slots in quarantine. */ |
| WRITE_ONCE(quarantine_batch_size, max((size_t)QUARANTINE_PERCPU_SIZE, |
| 2 * total_size / QUARANTINE_BATCHES)); |
| |
| if (likely(quarantine_size > quarantine_max_size)) { |
| qlist_move_all(&global_quarantine[quarantine_head], &to_free); |
| WRITE_ONCE(quarantine_size, quarantine_size - to_free.bytes); |
| quarantine_head++; |
| if (quarantine_head == QUARANTINE_BATCHES) |
| quarantine_head = 0; |
| } |
| |
| raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
| |
| qlist_free_all(&to_free, NULL); |
| srcu_read_unlock(&remove_cache_srcu, srcu_idx); |
| } |
| |
| static void qlist_move_cache(struct qlist_head *from, |
| struct qlist_head *to, |
| struct kmem_cache *cache) |
| { |
| struct qlist_node *curr; |
| |
| if (unlikely(qlist_empty(from))) |
| return; |
| |
| curr = from->head; |
| qlist_init(from); |
| while (curr) { |
| struct qlist_node *next = curr->next; |
| struct kmem_cache *obj_cache = qlink_to_cache(curr); |
| |
| if (obj_cache == cache) |
| qlist_put(to, curr, obj_cache->size); |
| else |
| qlist_put(from, curr, obj_cache->size); |
| |
| curr = next; |
| } |
| } |
| |
| static void per_cpu_remove_cache(void *arg) |
| { |
| struct kmem_cache *cache = arg; |
| struct qlist_head to_free = QLIST_INIT; |
| struct qlist_head *q; |
| |
| q = this_cpu_ptr(&cpu_quarantine); |
| /* |
| * Ensure the ordering between the writing to q->offline and |
| * per_cpu_remove_cache. Prevent cpu_quarantine from being corrupted |
| * by interrupt. |
| */ |
| if (READ_ONCE(q->offline)) |
| return; |
| qlist_move_cache(q, &to_free, cache); |
| qlist_free_all(&to_free, cache); |
| } |
| |
| /* Free all quarantined objects belonging to cache. */ |
| void kasan_quarantine_remove_cache(struct kmem_cache *cache) |
| { |
| unsigned long flags, i; |
| struct qlist_head to_free = QLIST_INIT; |
| |
| /* |
| * Must be careful to not miss any objects that are being moved from |
| * per-cpu list to the global quarantine in kasan_quarantine_put(), |
| * nor objects being freed in kasan_quarantine_reduce(). on_each_cpu() |
| * achieves the first goal, while synchronize_srcu() achieves the |
| * second. |
| */ |
| on_each_cpu(per_cpu_remove_cache, cache, 1); |
| |
| raw_spin_lock_irqsave(&quarantine_lock, flags); |
| for (i = 0; i < QUARANTINE_BATCHES; i++) { |
| if (qlist_empty(&global_quarantine[i])) |
| continue; |
| qlist_move_cache(&global_quarantine[i], &to_free, cache); |
| /* Scanning whole quarantine can take a while. */ |
| raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
| cond_resched(); |
| raw_spin_lock_irqsave(&quarantine_lock, flags); |
| } |
| raw_spin_unlock_irqrestore(&quarantine_lock, flags); |
| |
| qlist_free_all(&to_free, cache); |
| |
| synchronize_srcu(&remove_cache_srcu); |
| } |
| |
| static int kasan_cpu_online(unsigned int cpu) |
| { |
| this_cpu_ptr(&cpu_quarantine)->offline = false; |
| return 0; |
| } |
| |
| static int kasan_cpu_offline(unsigned int cpu) |
| { |
| struct qlist_head *q; |
| |
| q = this_cpu_ptr(&cpu_quarantine); |
| /* Ensure the ordering between the writing to q->offline and |
| * qlist_free_all. Otherwise, cpu_quarantine may be corrupted |
| * by interrupt. |
| */ |
| WRITE_ONCE(q->offline, true); |
| barrier(); |
| qlist_free_all(q, NULL); |
| return 0; |
| } |
| |
| static int __init kasan_cpu_quarantine_init(void) |
| { |
| int ret = 0; |
| |
| ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mm/kasan:online", |
| kasan_cpu_online, kasan_cpu_offline); |
| if (ret < 0) |
| pr_err("kasan cpu quarantine register failed [%d]\n", ret); |
| return ret; |
| } |
| late_initcall(kasan_cpu_quarantine_init); |