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-rw-r--r--mm/kasan/quarantine.c376
1 files changed, 376 insertions, 0 deletions
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
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+// 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.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ */
+
+#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);
+ unsigned long flags;
+
+ if (IS_ENABLED(CONFIG_SLAB))
+ local_irq_save(flags);
+
+ *(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);
+}
+
+void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
+{
+ unsigned long flags;
+ struct qlist_head *q;
+ struct qlist_head temp = QLIST_INIT;
+
+ /*
+ * Note: irq must be disabled until after we move the batch to the
+ * global quarantine. Otherwise quarantine_remove_cache() can miss
+ * some objects belonging to the cache if they are in our local temp
+ * list. 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;
+ }
+ qlist_put(q, &info->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);
+}
+
+void 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 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 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 quarantine_put(),
+ * nor objects being freed in 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);