security/ccsecurity/memory.c

/*
 * security/ccsecurity/memory.c
 *
 * Copyright (C) 2005-2012  NTT DATA CORPORATION
 *
 * Version: 1.8.3+   2015/04/21
 */

#include "internal.h"

/***** SECTION1: Constants definition *****/

/***** SECTION2: Structure definition *****/

/***** SECTION3: Prototype definition section *****/

bool ccs_memory_ok(const void *ptr, const unsigned int size);
const struct ccs_path_info *ccs_get_name(const char *name);
#ifdef CONFIG_CCSECURITY_USE_EXTERNAL_TASK_SECURITY
struct ccs_security *ccs_find_task_security(const struct task_struct *task);
#endif
void *ccs_commit_ok(void *data, const unsigned int size);
void __init ccs_mm_init(void);
void ccs_warn_oom(const char *function);

#ifdef CONFIG_CCSECURITY_USE_EXTERNAL_TASK_SECURITY
static int __ccs_alloc_task_security(const struct task_struct *task);
static void __ccs_free_task_security(const struct task_struct *task);
static void ccs_add_task_security(struct ccs_security *ptr,
                                  struct list_head *list);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 8)
static void ccs_rcu_free(struct rcu_head *rcu);
#else
static void ccs_rcu_free(void *arg);
#endif
#endif

/***** SECTION4: Standalone functions section *****/

/***** SECTION5: Variables definition section *****/

/* Memoy currently used by policy/audit log/query. */
unsigned int ccs_memory_used[CCS_MAX_MEMORY_STAT];

/* Memory quota for "policy"/"audit log"/"query". */
unsigned int ccs_memory_quota[CCS_MAX_MEMORY_STAT];

/* The list for "struct ccs_name". */
struct list_head ccs_name_list[CCS_MAX_HASH];

#ifdef CONFIG_CCSECURITY_USE_EXTERNAL_TASK_SECURITY

/* Dummy security context for avoiding NULL pointer dereference. */
static struct ccs_security ccs_oom_security = {
        .ccs_domain_info = &ccs_kernel_domain
};

/* Dummy security context for avoiding NULL pointer dereference. */
static struct ccs_security ccs_default_security = {
        .ccs_domain_info = &ccs_kernel_domain
};

/* List of "struct ccs_security". */
struct list_head ccs_task_security_list[CCS_MAX_TASK_SECURITY_HASH];
/* Lock for protecting ccs_task_security_list[]. */
static DEFINE_SPINLOCK(ccs_task_security_list_lock);

#endif

/***** SECTION6: Dependent functions section *****/

/**
 * ccs_warn_oom - Print out of memory warning message.
 *
 * @function: Function's name.
 *
 * Returns nothing.
 */
void ccs_warn_oom(const char *function)
{
        /* Reduce error messages. */
        static pid_t ccs_last_pid;
        const pid_t pid = current->pid;
        if (ccs_last_pid != pid) {
                printk(KERN_WARNING "ERROR: Out of memory at %s.\n",
                       function);
                ccs_last_pid = pid;
        }
        if (!ccs_policy_loaded)
                panic("MAC Initialization failed.\n");
}

/**
 * ccs_memory_ok - Check memory quota.
 *
 * @ptr:  Pointer to allocated memory. Maybe NULL.
 * @size: Size in byte. Not used if @ptr is NULL.
 *
 * Returns true if @ptr is not NULL and quota not exceeded, false otherwise.
 *
 * Caller holds ccs_policy_lock mutex.
 */
bool ccs_memory_ok(const void *ptr, const unsigned int size)
{
        if (ptr) {
                const size_t s = ccs_round2(size);
                ccs_memory_used[CCS_MEMORY_POLICY] += s;
                if (!ccs_memory_quota[CCS_MEMORY_POLICY] ||
                    ccs_memory_used[CCS_MEMORY_POLICY] <=
                    ccs_memory_quota[CCS_MEMORY_POLICY])
                        return true;
                ccs_memory_used[CCS_MEMORY_POLICY] -= s;
        }
        ccs_warn_oom(__func__);
        return false;
}

/**
 * ccs_commit_ok - Allocate memory and check memory quota.
 *
 * @data: Data to copy from.
 * @size: Size in byte.
 *
 * Returns pointer to allocated memory on success, NULL otherwise.
 * @data is zero-cleared on success.
 *
 * Caller holds ccs_policy_lock mutex.
 */
void *ccs_commit_ok(void *data, const unsigned int size)
{
        void *ptr = kmalloc(size, CCS_GFP_FLAGS);
        if (ccs_memory_ok(ptr, size)) {
                memmove(ptr, data, size);
                memset(data, 0, size);
                return ptr;
        }
        kfree(ptr);
        return NULL;
}

/**
 * ccs_get_name - Allocate memory for string data.
 *
 * @name: The string to store into the permernent memory.
 *
 * Returns pointer to "struct ccs_path_info" on success, NULL otherwise.
 */
const struct ccs_path_info *ccs_get_name(const char *name)
{
        struct ccs_name *ptr;
        unsigned int hash;
        int len;
        int allocated_len;
        struct list_head *head;

        if (!name)
                return NULL;
        len = strlen(name) + 1;
        hash = full_name_hash((const unsigned char *) name, len - 1);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 0) || defined(RHEL_MAJOR)
        head = &ccs_name_list[hash_long(hash, CCS_HASH_BITS)];
#else
        head = &ccs_name_list[hash % CCS_MAX_HASH];
#endif
        if (mutex_lock_interruptible(&ccs_policy_lock))
                return NULL;
        list_for_each_entry(ptr, head, head.list) {
                if (hash != ptr->entry.hash || strcmp(name, ptr->entry.name) ||
                    atomic_read(&ptr->head.users) == CCS_GC_IN_PROGRESS)
                        continue;
                atomic_inc(&ptr->head.users);
                goto out;
        }
        allocated_len = sizeof(*ptr) + len;
        ptr = kzalloc(allocated_len, CCS_GFP_FLAGS);
        if (ccs_memory_ok(ptr, allocated_len)) {
                ptr->entry.name = ((char *) ptr) + sizeof(*ptr);
                memmove((char *) ptr->entry.name, name, len);
                atomic_set(&ptr->head.users, 1);
                ccs_fill_path_info(&ptr->entry);
                ptr->size = allocated_len;
                list_add_tail(&ptr->head.list, head);
        } else {
                kfree(ptr);
                ptr = NULL;
        }
out:
        mutex_unlock(&ccs_policy_lock);
        return ptr ? &ptr->entry : NULL;
}

#ifdef CONFIG_CCSECURITY_USE_EXTERNAL_TASK_SECURITY

/**
 * ccs_add_task_security - Add "struct ccs_security" to list.
 *
 * @ptr:  Pointer to "struct ccs_security".
 * @list: Pointer to "struct list_head".
 *
 * Returns nothing.
 */
static void ccs_add_task_security(struct ccs_security *ptr,
                                  struct list_head *list)
{
        unsigned long flags;
        spin_lock_irqsave(&ccs_task_security_list_lock, flags);
        list_add_rcu(&ptr->list, list);
        spin_unlock_irqrestore(&ccs_task_security_list_lock, flags);
}

/**
 * __ccs_alloc_task_security - Allocate memory for new tasks.
 *
 * @task: Pointer to "struct task_struct".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int __ccs_alloc_task_security(const struct task_struct *task)
{
        struct ccs_security *old_security = ccs_current_security();
        struct ccs_security *new_security = kzalloc(sizeof(*new_security),
                                                    GFP_KERNEL);
        struct list_head *list = &ccs_task_security_list
                [hash_ptr((void *) task, CCS_TASK_SECURITY_HASH_BITS)];
        if (!new_security)
                return -ENOMEM;
        new_security->task = task;
        new_security->ccs_domain_info = old_security->ccs_domain_info;
        new_security->ccs_flags = old_security->ccs_flags;
        ccs_add_task_security(new_security, list);
        return 0;
}

/**
 * ccs_find_task_security - Find "struct ccs_security" for given task.
 *
 * @task: Pointer to "struct task_struct".
 *
 * Returns pointer to "struct ccs_security" on success, &ccs_oom_security on
 * out of memory, &ccs_default_security otherwise.
 *
 * If @task is current thread and "struct ccs_security" for current thread was
 * not found, I try to allocate it. But if allocation failed, current thread
 * will be killed by SIGKILL. Note that if current->pid == 1, sending SIGKILL
 * won't work.
 */
struct ccs_security *ccs_find_task_security(const struct task_struct *task)
{
        struct ccs_security *ptr;
        struct list_head *list = &ccs_task_security_list
                [hash_ptr((void *) task, CCS_TASK_SECURITY_HASH_BITS)];
        /* Make sure INIT_LIST_HEAD() in ccs_mm_init() takes effect. */
        while (!list->next);
        rcu_read_lock();
        list_for_each_entry_rcu(ptr, list, list) {
                if (ptr->task != task)
                        continue;
                rcu_read_unlock();
                return ptr;
        }
        rcu_read_unlock();
        if (task != current)
                return &ccs_default_security;
        /* Use GFP_ATOMIC because caller may have called rcu_read_lock(). */
        ptr = kzalloc(sizeof(*ptr), GFP_ATOMIC);
        if (!ptr) {
                printk(KERN_WARNING "Unable to allocate memory for pid=%u\n",
                       task->pid);
                send_sig(SIGKILL, current, 0);
                return &ccs_oom_security;
        }
        *ptr = ccs_default_security;
        ptr->task = task;
        ccs_add_task_security(ptr, list);
        return ptr;
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 8)

/**
 * ccs_rcu_free - RCU callback for releasing "struct ccs_security".
 *
 * @rcu: Pointer to "struct rcu_head".
 *
 * Returns nothing.
 */
static void ccs_rcu_free(struct rcu_head *rcu)
{
        struct ccs_security *ptr = container_of(rcu, typeof(*ptr), rcu);
        kfree(ptr);
}

#else

/**
 * ccs_rcu_free - RCU callback for releasing "struct ccs_security".
 *
 * @arg: Pointer to "void".
 *
 * Returns nothing.
 */
static void ccs_rcu_free(void *arg)
{
        struct ccs_security *ptr = arg;
        kfree(ptr);
}

#endif

/**
 * __ccs_free_task_security - Release memory associated with "struct task_struct".
 *
 * @task: Pointer to "struct task_struct".
 *
 * Returns nothing.
 */
static void __ccs_free_task_security(const struct task_struct *task)
{
        unsigned long flags;
        struct ccs_security *ptr = ccs_find_task_security(task);
        if (ptr == &ccs_default_security || ptr == &ccs_oom_security)
                return;
        spin_lock_irqsave(&ccs_task_security_list_lock, flags);
        list_del_rcu(&ptr->list);
        spin_unlock_irqrestore(&ccs_task_security_list_lock, flags);
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 8)
        call_rcu(&ptr->rcu, ccs_rcu_free);
#else
        call_rcu(&ptr->rcu, ccs_rcu_free, ptr);
#endif
}

#endif

/**
 * ccs_mm_init - Initialize mm related code.
 *
 * Returns nothing.
 */
void __init ccs_mm_init(void)
{
        int idx;
        for (idx = 0; idx < CCS_MAX_HASH; idx++)
                INIT_LIST_HEAD(&ccs_name_list[idx]);
#ifdef CONFIG_CCSECURITY_USE_EXTERNAL_TASK_SECURITY
        for (idx = 0; idx < CCS_MAX_TASK_SECURITY_HASH; idx++)
                INIT_LIST_HEAD(&ccs_task_security_list[idx]);
#endif
        smp_wmb(); /* Avoid out of order execution. */
#ifdef CONFIG_CCSECURITY_USE_EXTERNAL_TASK_SECURITY
        ccsecurity_ops.alloc_task_security = __ccs_alloc_task_security;
        ccsecurity_ops.free_task_security = __ccs_free_task_security;
#endif
        ccs_kernel_domain.domainname = ccs_get_name("<kernel>");
        list_add_tail_rcu(&ccs_kernel_domain.list, &ccs_domain_list);
}