- 根目录:
- security
- selinux
- avc.c
/*
* Implementation of the kernel access vector cache (AVC).
*
* Authors: Stephen Smalley, <sds@epoch.ncsc.mil>
* James Morris <jmorris@redhat.com>
*
* Update: KaiGai, Kohei <kaigai@ak.jp.nec.com>
* Replaced the avc_lock spinlock by RCU.
*
* Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@redhat.com>
*
* 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.
*/
#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/dcache.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/percpu.h>
#include <linux/list.h>
#include <net/sock.h>
#include <linux/un.h>
#include <net/af_unix.h>
#include <linux/ip.h>
#include <linux/audit.h>
#include <linux/ipv6.h>
#include <net/ipv6.h>
#include "avc.h"
#include "avc_ss.h"
#include "classmap.h"
#define AVC_CACHE_SLOTS 512
#define AVC_DEF_CACHE_THRESHOLD 512
#define AVC_CACHE_RECLAIM 16
#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
#define avc_cache_stats_incr(field) this_cpu_inc(avc_cache_stats.field)
#else
#define avc_cache_stats_incr(field) do {} while (0)
#endif
struct avc_entry {
u32 ssid;
u32 tsid;
u16 tclass;
struct av_decision avd;
struct avc_xperms_node *xp_node;
};
struct avc_node {
struct avc_entry ae;
struct hlist_node list; /* anchored in avc_cache->slots[i] */
struct rcu_head rhead;
};
struct avc_xperms_decision_node {
struct extended_perms_decision xpd;
struct list_head xpd_list; /* list of extended_perms_decision */
};
struct avc_xperms_node {
struct extended_perms xp;
struct list_head xpd_head; /* list head of extended_perms_decision */
};
struct avc_cache {
struct hlist_head slots[AVC_CACHE_SLOTS]; /* head for avc_node->list */
spinlock_t slots_lock[AVC_CACHE_SLOTS]; /* lock for writes */
atomic_t lru_hint; /* LRU hint for reclaim scan */
atomic_t active_nodes;
u32 latest_notif; /* latest revocation notification */
};
struct avc_callback_node {
int (*callback) (u32 event, u32 ssid, u32 tsid,
u16 tclass, u32 perms,
u32 *out_retained);
u32 events;
u32 ssid;
u32 tsid;
u16 tclass;
u32 perms;
struct avc_callback_node *next;
};
/* Exported via selinufs */
unsigned int avc_cache_threshold = AVC_DEF_CACHE_THRESHOLD;
#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS
DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };
#endif
static struct avc_cache avc_cache;
static struct avc_callback_node *avc_callbacks;
static struct kmem_cache *avc_node_cachep;
static struct kmem_cache *avc_xperms_data_cachep;
static struct kmem_cache *avc_xperms_decision_cachep;
static struct kmem_cache *avc_xperms_cachep;
static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
{
return (ssid ^ (tsid<<2) ^ (tclass<<4)) & (AVC_CACHE_SLOTS - 1);
}
/**
* avc_dump_av - Display an access vector in human-readable form.
* @tclass: target security class
* @av: access vector
*/
static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
{
const char **perms;
int i, perm;
if (av == 0) {
audit_log_format(ab, " null");
return;
}
perms = secclass_map[tclass-1].perms;
audit_log_format(ab, " {");
i = 0;
perm = 1;
while (i < (sizeof(av) * 8)) {
if ((perm & av) && perms[i]) {
audit_log_format(ab, " %s", perms[i]);
av &= ~perm;
}
i++;
perm <<= 1;
}
if (av)
audit_log_format(ab, " 0x%x", av);
audit_log_format(ab, " }");
}
/**
* avc_dump_query - Display a SID pair and a class in human-readable form.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
*/
static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tclass)
{
int rc;
char *scontext;
u32 scontext_len;
rc = security_sid_to_context(ssid, &scontext, &scontext_len);
if (rc)
audit_log_format(ab, "ssid=%d", ssid);
else {
audit_log_format(ab, "scontext=%s", scontext);
kfree(scontext);
}
rc = security_sid_to_context(tsid, &scontext, &scontext_len);
if (rc)
audit_log_format(ab, " tsid=%d", tsid);
else {
audit_log_format(ab, " tcontext=%s", scontext);
kfree(scontext);
}
BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
}
/**
* avc_init - Initialize the AVC.
*
* Initialize the access vector cache.
*/
void __init avc_init(void)
{
int i;
for (i = 0; i < AVC_CACHE_SLOTS; i++) {
INIT_HLIST_HEAD(&avc_cache.slots[i]);
spin_lock_init(&avc_cache.slots_lock[i]);
}
atomic_set(&avc_cache.active_nodes, 0);
atomic_set(&avc_cache.lru_hint, 0);
avc_node_cachep = kmem_cache_create("avc_node", sizeof(struct avc_node),
0, SLAB_PANIC, NULL);
avc_xperms_cachep = kmem_cache_create("avc_xperms_node",
sizeof(struct avc_xperms_node),
0, SLAB_PANIC, NULL);
avc_xperms_decision_cachep = kmem_cache_create(
"avc_xperms_decision_node",
sizeof(struct avc_xperms_decision_node),
0, SLAB_PANIC, NULL);
avc_xperms_data_cachep = kmem_cache_create("avc_xperms_data",
sizeof(struct extended_perms_data),
0, SLAB_PANIC, NULL);
audit_log(current->audit_context, GFP_KERNEL, AUDIT_KERNEL, "AVC INITIALIZED\n");
}
int avc_get_hash_stats(char *page)
{
int i, chain_len, max_chain_len, slots_used;
struct avc_node *node;
struct hlist_head *head;
rcu_read_lock();
slots_used = 0;
max_chain_len = 0;
for (i = 0; i < AVC_CACHE_SLOTS; i++) {
head = &avc_cache.slots[i];
if (!hlist_empty(head)) {
struct hlist_node *next;
slots_used++;
chain_len = 0;
hlist_for_each_entry_rcu(node, next, head, list)
chain_len++;
if (chain_len > max_chain_len)
max_chain_len = chain_len;
}
}
rcu_read_unlock();
return scnprintf(page, PAGE_SIZE, "entries: %d\nbuckets used: %d/%d\n"
"longest chain: %d\n",
atomic_read(&avc_cache.active_nodes),
slots_used, AVC_CACHE_SLOTS, max_chain_len);
}
/*
* using a linked list for extended_perms_decision lookup because the list is
* always small. i.e. less than 5, typically 1
*/
static struct extended_perms_decision *avc_xperms_decision_lookup(u8 driver,
struct avc_xperms_node *xp_node)
{
struct avc_xperms_decision_node *xpd_node;
list_for_each_entry(xpd_node, &xp_node->xpd_head, xpd_list) {
if (xpd_node->xpd.driver == driver)
return &xpd_node->xpd;
}
return NULL;
}
static inline unsigned int
avc_xperms_has_perm(struct extended_perms_decision *xpd,
u8 perm, u8 which)
{
unsigned int rc = 0;
if ((which == XPERMS_ALLOWED) &&
(xpd->used & XPERMS_ALLOWED))
rc = security_xperm_test(xpd->allowed->p, perm);
else if ((which == XPERMS_AUDITALLOW) &&
(xpd->used & XPERMS_AUDITALLOW))
rc = security_xperm_test(xpd->auditallow->p, perm);
else if ((which == XPERMS_DONTAUDIT) &&
(xpd->used & XPERMS_DONTAUDIT))
rc = security_xperm_test(xpd->dontaudit->p, perm);
return rc;
}
static void avc_xperms_allow_perm(struct avc_xperms_node *xp_node,
u8 driver, u8 perm)
{
struct extended_perms_decision *xpd;
security_xperm_set(xp_node->xp.drivers.p, driver);
xpd = avc_xperms_decision_lookup(driver, xp_node);
if (xpd && xpd->allowed)
security_xperm_set(xpd->allowed->p, perm);
}
static void avc_xperms_decision_free(struct avc_xperms_decision_node *xpd_node)
{
struct extended_perms_decision *xpd;
xpd = &xpd_node->xpd;
if (xpd->allowed)
kmem_cache_free(avc_xperms_data_cachep, xpd->allowed);
if (xpd->auditallow)
kmem_cache_free(avc_xperms_data_cachep, xpd->auditallow);
if (xpd->dontaudit)
kmem_cache_free(avc_xperms_data_cachep, xpd->dontaudit);
kmem_cache_free(avc_xperms_decision_cachep, xpd_node);
}
static void avc_xperms_free(struct avc_xperms_node *xp_node)
{
struct avc_xperms_decision_node *xpd_node, *tmp;
if (!xp_node)
return;
list_for_each_entry_safe(xpd_node, tmp, &xp_node->xpd_head, xpd_list) {
list_del(&xpd_node->xpd_list);
avc_xperms_decision_free(xpd_node);
}
kmem_cache_free(avc_xperms_cachep, xp_node);
}
static void avc_copy_xperms_decision(struct extended_perms_decision *dest,
struct extended_perms_decision *src)
{
dest->driver = src->driver;
dest->used = src->used;
if (dest->used & XPERMS_ALLOWED)
memcpy(dest->allowed->p, src->allowed->p,
sizeof(src->allowed->p));
if (dest->used & XPERMS_AUDITALLOW)
memcpy(dest->auditallow->p, src->auditallow->p,
sizeof(src->auditallow->p));
if (dest->used & XPERMS_DONTAUDIT)
memcpy(dest->dontaudit->p, src->dontaudit->p,
sizeof(src->dontaudit->p));
}
/*
* similar to avc_copy_xperms_decision, but only copy decision
* information relevant to this perm
*/
static inline void avc_quick_copy_xperms_decision(u8 perm,
struct extended_perms_decision *dest,
struct extended_perms_decision *src)
{
/*
* compute index of the u32 of the 256 bits (8 u32s) that contain this
* command permission
*/
u8 i = perm >> 5;
dest->used = src->used;
if (dest->used & XPERMS_ALLOWED)
dest->allowed->p[i] = src->allowed->p[i];
if (dest->used & XPERMS_AUDITALLOW)
dest->auditallow->p[i] = src->auditallow->p[i];
if (dest->used & XPERMS_DONTAUDIT)
dest->dontaudit->p[i] = src->dontaudit->p[i];
}
static struct avc_xperms_decision_node
*avc_xperms_decision_alloc(u8 which)
{
struct avc_xperms_decision_node *xpd_node;
struct extended_perms_decision *xpd;
xpd_node = kmem_cache_zalloc(avc_xperms_decision_cachep,
GFP_ATOMIC | __GFP_NOMEMALLOC);
if (!xpd_node)
return NULL;
xpd = &xpd_node->xpd;
if (which & XPERMS_ALLOWED) {
xpd->allowed = kmem_cache_zalloc(avc_xperms_data_cachep,
GFP_ATOMIC | __GFP_NOMEMALLOC);
if (!xpd->allowed)
goto error;
}
if (which & XPERMS_AUDITALLOW) {
xpd->auditallow = kmem_cache_zalloc(avc_xperms_data_cachep,
GFP_ATOMIC | __GFP_NOMEMALLOC);
if (!xpd->auditallow)
goto error;
}
if (which & XPERMS_DONTAUDIT) {
xpd->dontaudit = kmem_cache_zalloc(avc_xperms_data_cachep,
GFP_ATOMIC | __GFP_NOMEMALLOC);
if (!xpd->dontaudit)
goto error;
}
return xpd_node;
error:
avc_xperms_decision_free(xpd_node);
return NULL;
}
static int avc_add_xperms_decision(struct avc_node *node,
struct extended_perms_decision *src)
{
struct avc_xperms_decision_node *dest_xpd;
node->ae.xp_node->xp.len++;
dest_xpd = avc_xperms_decision_alloc(src->used);
if (!dest_xpd)
return -ENOMEM;
avc_copy_xperms_decision(&dest_xpd->xpd, src);
list_add(&dest_xpd->xpd_list, &node->ae.xp_node->xpd_head);
return 0;
}
static struct avc_xperms_node *avc_xperms_alloc(void)
{
struct avc_xperms_node *xp_node;
xp_node = kmem_cache_zalloc(avc_xperms_cachep,
GFP_ATOMIC|__GFP_NOMEMALLOC);
if (!xp_node)
return xp_node;
INIT_LIST_HEAD(&xp_node->xpd_head);
return xp_node;
}
static int avc_xperms_populate(struct avc_node *node,
struct avc_xperms_node *src)
{
struct avc_xperms_node *dest;
struct avc_xperms_decision_node *dest_xpd;
struct avc_xperms_decision_node *src_xpd;
if (src->xp.len == 0)
return 0;
dest = avc_xperms_alloc();
if (!dest)
return -ENOMEM;
memcpy(dest->xp.drivers.p, src->xp.drivers.p, sizeof(dest->xp.drivers.p));
dest->xp.len = src->xp.len;
/* for each source xpd allocate a destination xpd and copy */
list_for_each_entry(src_xpd, &src->xpd_head, xpd_list) {
dest_xpd = avc_xperms_decision_alloc(src_xpd->xpd.used);
if (!dest_xpd)
goto error;
avc_copy_xperms_decision(&dest_xpd->xpd, &src_xpd->xpd);
list_add(&dest_xpd->xpd_list, &dest->xpd_head);
}
node->ae.xp_node = dest;
return 0;
error:
avc_xperms_free(dest);
return -ENOMEM;
}
static inline u32 avc_xperms_audit_required(u32 requested,
struct av_decision *avd,
struct extended_perms_decision *xpd,
u8 perm,
int result,
u32 *deniedp)
{
u32 denied, audited;
denied = requested & ~avd->allowed;
if (unlikely(denied)) {
audited = denied & avd->auditdeny;
if (audited && xpd) {
if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
audited &= ~requested;
}
} else if (result) {
audited = denied = requested;
} else {
audited = requested & avd->auditallow;
if (audited && xpd) {
if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
audited &= ~requested;
}
}
*deniedp = denied;
return audited;
}
static void avc_node_free(struct rcu_head *rhead)
{
struct avc_node *node = container_of(rhead, struct avc_node, rhead);
avc_xperms_free(node->ae.xp_node);
kmem_cache_free(avc_node_cachep, node);
avc_cache_stats_incr(frees);
}
static void avc_node_delete(struct avc_node *node)
{
hlist_del_rcu(&node->list);
call_rcu(&node->rhead, avc_node_free);
atomic_dec(&avc_cache.active_nodes);
}
static void avc_node_kill(struct avc_node *node)
{
avc_xperms_free(node->ae.xp_node);
kmem_cache_free(avc_node_cachep, node);
avc_cache_stats_incr(frees);
atomic_dec(&avc_cache.active_nodes);
}
static void avc_node_replace(struct avc_node *new, struct avc_node *old)
{
hlist_replace_rcu(&old->list, &new->list);
call_rcu(&old->rhead, avc_node_free);
atomic_dec(&avc_cache.active_nodes);
}
static inline int avc_reclaim_node(void)
{
struct avc_node *node;
int hvalue, try, ecx;
unsigned long flags;
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;
for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++) {
hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
head = &avc_cache.slots[hvalue];
lock = &avc_cache.slots_lock[hvalue];
if (!spin_trylock_irqsave(lock, flags))
continue;
rcu_read_lock();
hlist_for_each_entry(node, next, head, list) {
avc_node_delete(node);
avc_cache_stats_incr(reclaims);
ecx++;
if (ecx >= AVC_CACHE_RECLAIM) {
rcu_read_unlock();
spin_unlock_irqrestore(lock, flags);
goto out;
}
}
rcu_read_unlock();
spin_unlock_irqrestore(lock, flags);
}
out:
return ecx;
}
static struct avc_node *avc_alloc_node(void)
{
struct avc_node *node;
node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
if (!node)
goto out;
INIT_HLIST_NODE(&node->list);
avc_cache_stats_incr(allocations);
if (atomic_inc_return(&avc_cache.active_nodes) > avc_cache_threshold)
avc_reclaim_node();
out:
return node;
}
static void avc_node_populate(struct avc_node *node, u32 ssid, u32 tsid, u16 tclass, struct av_decision *avd)
{
node->ae.ssid = ssid;
node->ae.tsid = tsid;
node->ae.tclass = tclass;
memcpy(&node->ae.avd, avd, sizeof(node->ae.avd));
}
static inline struct avc_node *avc_search_node(u32 ssid, u32 tsid, u16 tclass)
{
struct avc_node *node, *ret = NULL;
int hvalue;
struct hlist_head *head;
struct hlist_node *next;
hvalue = avc_hash(ssid, tsid, tclass);
head = &avc_cache.slots[hvalue];
hlist_for_each_entry_rcu(node, next, head, list) {
if (ssid == node->ae.ssid &&
tclass == node->ae.tclass &&
tsid == node->ae.tsid) {
ret = node;
break;
}
}
return ret;
}
/**
* avc_lookup - Look up an AVC entry.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
*
* Look up an AVC entry that is valid for the
* (@ssid, @tsid), interpreting the permissions
* based on @tclass. If a valid AVC entry exists,
* then this function returns the avc_node.
* Otherwise, this function returns NULL.
*/
static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass)
{
struct avc_node *node;
avc_cache_stats_incr(lookups);
node = avc_search_node(ssid, tsid, tclass);
if (node)
return node;
avc_cache_stats_incr(misses);
return NULL;
}
static int avc_latest_notif_update(int seqno, int is_insert)
{
int ret = 0;
static DEFINE_SPINLOCK(notif_lock);
unsigned long flag;
spin_lock_irqsave(¬if_lock, flag);
if (is_insert) {
if (seqno < avc_cache.latest_notif) {
printk(KERN_WARNING "SELinux: avc: seqno %d < latest_notif %d\n",
seqno, avc_cache.latest_notif);
ret = -EAGAIN;
}
} else {
if (seqno > avc_cache.latest_notif)
avc_cache.latest_notif = seqno;
}
spin_unlock_irqrestore(¬if_lock, flag);
return ret;
}
/**
* avc_insert - Insert an AVC entry.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @avd: resulting av decision
* @xp_node: resulting extended permissions
*
* Insert an AVC entry for the SID pair
* (@ssid, @tsid) and class @tclass.
* The access vectors and the sequence number are
* normally provided by the security server in
* response to a security_compute_av() call. If the
* sequence number @avd->seqno is not less than the latest
* revocation notification, then the function copies
* the access vectors into a cache entry, returns
* avc_node inserted. Otherwise, this function returns NULL.
*/
static struct avc_node *avc_insert(u32 ssid, u32 tsid, u16 tclass,
struct av_decision *avd,
struct avc_xperms_node *xp_node)
{
struct avc_node *pos, *node = NULL;
int hvalue;
unsigned long flag;
if (avc_latest_notif_update(avd->seqno, 1))
goto out;
node = avc_alloc_node();
if (node) {
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;
int rc = 0;
hvalue = avc_hash(ssid, tsid, tclass);
avc_node_populate(node, ssid, tsid, tclass, avd);
rc = avc_xperms_populate(node, xp_node);
if (rc) {
kmem_cache_free(avc_node_cachep, node);
return NULL;
}
head = &avc_cache.slots[hvalue];
lock = &avc_cache.slots_lock[hvalue];
spin_lock_irqsave(lock, flag);
hlist_for_each_entry(pos, next, head, list) {
if (pos->ae.ssid == ssid &&
pos->ae.tsid == tsid &&
pos->ae.tclass == tclass) {
avc_node_replace(node, pos);
goto found;
}
}
hlist_add_head_rcu(&node->list, head);
found:
spin_unlock_irqrestore(lock, flag);
}
out:
return node;
}
/**
* avc_audit_pre_callback - SELinux specific information
* will be called by generic audit code
* @ab: the audit buffer
* @a: audit_data
*/
static void avc_audit_pre_callback(struct audit_buffer *ab, void *a)
{
struct common_audit_data *ad = a;
audit_log_format(ab, "avc: %s ",
ad->selinux_audit_data->slad->denied ? "denied" : "granted");
avc_dump_av(ab, ad->selinux_audit_data->slad->tclass,
ad->selinux_audit_data->slad->audited);
audit_log_format(ab, " for ");
}
/**
* avc_audit_post_callback - SELinux specific information
* will be called by generic audit code
* @ab: the audit buffer
* @a: audit_data
*/
static void avc_audit_post_callback(struct audit_buffer *ab, void *a)
{
struct common_audit_data *ad = a;
audit_log_format(ab, " ");
avc_dump_query(ab, ad->selinux_audit_data->slad->ssid,
ad->selinux_audit_data->slad->tsid,
ad->selinux_audit_data->slad->tclass);
if (ad->selinux_audit_data->slad->denied) {
audit_log_format(ab, " permissive=%u",
ad->selinux_audit_data->slad->result ? 0 : 1);
}
}
/* This is the slow part of avc audit with big stack footprint */
static noinline int slow_avc_audit(u32 ssid, u32 tsid, u16 tclass,
u32 requested, u32 audited, u32 denied, int result,
struct common_audit_data *a,
unsigned flags)
{
struct common_audit_data stack_data;
struct selinux_audit_data sad = {0,};
struct selinux_late_audit_data slad;
if (!a) {
a = &stack_data;
COMMON_AUDIT_DATA_INIT(a, NONE);
a->selinux_audit_data = &sad;
}
/*
* When in a RCU walk do the audit on the RCU retry. This is because
* the collection of the dname in an inode audit message is not RCU
* safe. Note this may drop some audits when the situation changes
* during retry. However this is logically just as if the operation
* happened a little later.
*/
if ((a->type == LSM_AUDIT_DATA_INODE) &&
(flags & MAY_NOT_BLOCK))
return -ECHILD;
slad.tclass = tclass;
slad.requested = requested;
slad.ssid = ssid;
slad.tsid = tsid;
slad.audited = audited;
slad.denied = denied;
slad.result = result;
a->selinux_audit_data->slad = &slad;
common_lsm_audit(a, avc_audit_pre_callback, avc_audit_post_callback);
return 0;
}
static inline int avc_xperms_audit(u32 ssid, u32 tsid, u16 tclass,
u32 requested, struct av_decision *avd,
struct extended_perms_decision *xpd,
u8 perm, int result,
struct common_audit_data *ad)
{
u32 audited, denied;
audited = avc_xperms_audit_required(
requested, avd, xpd, perm, result, &denied);
if (likely(!audited))
return 0;
return slow_avc_audit(ssid, tsid, tclass, requested,
audited, denied, result, ad, 0);
}
/**
* avc_audit - Audit the granting or denial of permissions.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @requested: requested permissions
* @avd: access vector decisions
* @result: result from avc_has_perm_noaudit
* @a: auxiliary audit data
* @flags: VFS walk flags
*
* Audit the granting or denial of permissions in accordance
* with the policy. This function is typically called by
* avc_has_perm() after a permission check, but can also be
* called directly by callers who use avc_has_perm_noaudit()
* in order to separate the permission check from the auditing.
* For example, this separation is useful when the permission check must
* be performed under a lock, to allow the lock to be released
* before calling the auditing code.
*/
inline int avc_audit(u32 ssid, u32 tsid,
u16 tclass, u32 requested,
struct av_decision *avd, int result, struct common_audit_data *a,
unsigned flags)
{
u32 denied, audited;
denied = requested & ~avd->allowed;
if (unlikely(denied)) {
audited = denied & avd->auditdeny;
/*
* a->selinux_audit_data->auditdeny is TRICKY! Setting a bit in
* this field means that ANY denials should NOT be audited if
* the policy contains an explicit dontaudit rule for that
* permission. Take notice that this is unrelated to the
* actual permissions that were denied. As an example lets
* assume:
*
* denied == READ
* avd.auditdeny & ACCESS == 0 (not set means explicit rule)
* selinux_audit_data->auditdeny & ACCESS == 1
*
* We will NOT audit the denial even though the denied
* permission was READ and the auditdeny checks were for
* ACCESS
*/
if (a &&
a->selinux_audit_data->auditdeny &&
!(a->selinux_audit_data->auditdeny & avd->auditdeny))
audited = 0;
} else if (result)
audited = denied = requested;
else
audited = requested & avd->auditallow;
if (likely(!audited))
return 0;
return slow_avc_audit(ssid, tsid, tclass,
requested, audited, denied, result,
a, flags);
}
/**
* avc_add_callback - Register a callback for security events.
* @callback: callback function
* @events: security events
* @ssid: source security identifier or %SECSID_WILD
* @tsid: target security identifier or %SECSID_WILD
* @tclass: target security class
* @perms: permissions
*
* Register a callback function for events in the set @events
* related to the SID pair (@ssid, @tsid)
* and the permissions @perms, interpreting
* @perms based on @tclass. Returns %0 on success or
* -%ENOMEM if insufficient memory exists to add the callback.
*/
int avc_add_callback(int (*callback)(u32 event, u32 ssid, u32 tsid,
u16 tclass, u32 perms,
u32 *out_retained),
u32 events, u32 ssid, u32 tsid,
u16 tclass, u32 perms)
{
struct avc_callback_node *c;
int rc = 0;
c = kmalloc(sizeof(*c), GFP_ATOMIC);
if (!c) {
rc = -ENOMEM;
goto out;
}
c->callback = callback;
c->events = events;
c->ssid = ssid;
c->tsid = tsid;
c->perms = perms;
c->next = avc_callbacks;
avc_callbacks = c;
out:
return rc;
}
static inline int avc_sidcmp(u32 x, u32 y)
{
return (x == y || x == SECSID_WILD || y == SECSID_WILD);
}
/**
* avc_update_node Update an AVC entry
* @event : Updating event
* @perms : Permission mask bits
* @ssid,@tsid,@tclass : identifier of an AVC entry
* @seqno : sequence number when decision was made
* @xpd: extended_perms_decision to be added to the node
*
* if a valid AVC entry doesn't exist,this function returns -ENOENT.
* if kmalloc() called internal returns NULL, this function returns -ENOMEM.
* otherwise, this function updates the AVC entry. The original AVC-entry object
* will release later by RCU.
*/
static int avc_update_node(u32 event, u32 perms, u8 driver, u8 xperm, u32 ssid,
u32 tsid, u16 tclass, u32 seqno,
struct extended_perms_decision *xpd,
u32 flags)
{
int hvalue, rc = 0;
unsigned long flag;
struct avc_node *pos, *node, *orig = NULL;
struct hlist_head *head;
struct hlist_node *next;
spinlock_t *lock;
node = avc_alloc_node();
if (!node) {
rc = -ENOMEM;
goto out;
}
/* Lock the target slot */
hvalue = avc_hash(ssid, tsid, tclass);
head = &avc_cache.slots[hvalue];
lock = &avc_cache.slots_lock[hvalue];
spin_lock_irqsave(lock, flag);
hlist_for_each_entry(pos, next, head, list) {
if (ssid == pos->ae.ssid &&
tsid == pos->ae.tsid &&
tclass == pos->ae.tclass &&
seqno == pos->ae.avd.seqno){
orig = pos;
break;
}
}
if (!orig) {
rc = -ENOENT;
avc_node_kill(node);
goto out_unlock;
}
/*
* Copy and replace original node.
*/
avc_node_populate(node, ssid, tsid, tclass, &orig->ae.avd);
if (orig->ae.xp_node) {
rc = avc_xperms_populate(node, orig->ae.xp_node);
if (rc) {
kmem_cache_free(avc_node_cachep, node);
goto out_unlock;
}
}
switch (event) {
case AVC_CALLBACK_GRANT:
node->ae.avd.allowed |= perms;
if (node->ae.xp_node && (flags & AVC_EXTENDED_PERMS))
avc_xperms_allow_perm(node->ae.xp_node, driver, xperm);
break;
case AVC_CALLBACK_TRY_REVOKE:
case AVC_CALLBACK_REVOKE:
node->ae.avd.allowed &= ~perms;
break;
case AVC_CALLBACK_AUDITALLOW_ENABLE:
node->ae.avd.auditallow |= perms;
break;
case AVC_CALLBACK_AUDITALLOW_DISABLE:
node->ae.avd.auditallow &= ~perms;
break;
case AVC_CALLBACK_AUDITDENY_ENABLE:
node->ae.avd.auditdeny |= perms;
break;
case AVC_CALLBACK_AUDITDENY_DISABLE:
node->ae.avd.auditdeny &= ~perms;
break;
case AVC_CALLBACK_ADD_XPERMS:
avc_add_xperms_decision(node, xpd);
break;
}
avc_node_replace(node, orig);
out_unlock:
spin_unlock_irqrestore(lock, flag);
out:
return rc;
}
/**
* avc_flush - Flush the cache
*/
static void avc_flush(void)
{
struct hlist_head *head;
struct hlist_node *next;
struct avc_node *node;
spinlock_t *lock;
unsigned long flag;
int i;
for (i = 0; i < AVC_CACHE_SLOTS; i++) {
head = &avc_cache.slots[i];
lock = &avc_cache.slots_lock[i];
spin_lock_irqsave(lock, flag);
/*
* With preemptable RCU, the outer spinlock does not
* prevent RCU grace periods from ending.
*/
rcu_read_lock();
hlist_for_each_entry(node, next, head, list)
avc_node_delete(node);
rcu_read_unlock();
spin_unlock_irqrestore(lock, flag);
}
}
/**
* avc_ss_reset - Flush the cache and revalidate migrated permissions.
* @seqno: policy sequence number
*/
int avc_ss_reset(u32 seqno)
{
struct avc_callback_node *c;
int rc = 0, tmprc;
avc_flush();
for (c = avc_callbacks; c; c = c->next) {
if (c->events & AVC_CALLBACK_RESET) {
tmprc = c->callback(AVC_CALLBACK_RESET,
0, 0, 0, 0, NULL);
/* save the first error encountered for the return
value and continue processing the callbacks */
if (!rc)
rc = tmprc;
}
}
avc_latest_notif_update(seqno, 0);
return rc;
}
/*
* Slow-path helper function for avc_has_perm_noaudit,
* when the avc_node lookup fails. We get called with
* the RCU read lock held, and need to return with it
* still held, but drop if for the security compute.
*
* Don't inline this, since it's the slow-path and just
* results in a bigger stack frame.
*/
static noinline struct avc_node *avc_compute_av(u32 ssid, u32 tsid,
u16 tclass, struct av_decision *avd,
struct avc_xperms_node *xp_node)
{
rcu_read_unlock();
INIT_LIST_HEAD(&xp_node->xpd_head);
security_compute_av(ssid, tsid, tclass, avd, &xp_node->xp);
rcu_read_lock();
return avc_insert(ssid, tsid, tclass, avd, xp_node);
}
static noinline int avc_denied(u32 ssid, u32 tsid,
u16 tclass, u32 requested,
u8 driver, u8 xperm, unsigned flags,
struct av_decision *avd)
{
if (flags & AVC_STRICT)
return -EACCES;
if (selinux_enforcing && !(avd->flags & AVD_FLAGS_PERMISSIVE))
return -EACCES;
avc_update_node(AVC_CALLBACK_GRANT, requested, driver, xperm, ssid,
tsid, tclass, avd->seqno, NULL, flags);
return 0;
}
/*
* The avc extended permissions logic adds an additional 256 bits of
* permissions to an avc node when extended permissions for that node are
* specified in the avtab. If the additional 256 permissions is not adequate,
* as-is the case with ioctls, then multiple may be chained together and the
* driver field is used to specify which set contains the permission.
*/
int avc_has_extended_perms(u32 ssid, u32 tsid, u16 tclass, u32 requested,
u8 driver, u8 xperm, struct common_audit_data *ad)
{
struct avc_node *node;
struct av_decision avd;
u32 denied;
struct extended_perms_decision local_xpd;
struct extended_perms_decision *xpd = NULL;
struct extended_perms_data allowed;
struct extended_perms_data auditallow;
struct extended_perms_data dontaudit;
struct avc_xperms_node local_xp_node;
struct avc_xperms_node *xp_node;
int rc = 0, rc2;
xp_node = &local_xp_node;
BUG_ON(!requested);
rcu_read_lock();
node = avc_lookup(ssid, tsid, tclass);
if (unlikely(!node)) {
node = avc_compute_av(ssid, tsid, tclass, &avd, xp_node);
} else {
memcpy(&avd, &node->ae.avd, sizeof(avd));
xp_node = node->ae.xp_node;
}
/* if extended permissions are not defined, only consider av_decision */
if (!xp_node || !xp_node->xp.len)
goto decision;
local_xpd.allowed = &allowed;
local_xpd.auditallow = &auditallow;
local_xpd.dontaudit = &dontaudit;
xpd = avc_xperms_decision_lookup(driver, xp_node);
if (unlikely(!xpd)) {
/*
* Compute the extended_perms_decision only if the driver
* is flagged
*/
if (!security_xperm_test(xp_node->xp.drivers.p, driver)) {
avd.allowed &= ~requested;
goto decision;
}
rcu_read_unlock();
security_compute_xperms_decision(ssid, tsid, tclass, driver,
&local_xpd);
rcu_read_lock();
avc_update_node(AVC_CALLBACK_ADD_XPERMS, requested, driver, xperm,
ssid, tsid, tclass, avd.seqno, &local_xpd, 0);
} else {
avc_quick_copy_xperms_decision(xperm, &local_xpd, xpd);
}
xpd = &local_xpd;
if (!avc_xperms_has_perm(xpd, xperm, XPERMS_ALLOWED))
avd.allowed &= ~requested;
decision:
denied = requested & ~(avd.allowed);
if (unlikely(denied))
rc = avc_denied(ssid, tsid, tclass, requested, driver, xperm,
AVC_EXTENDED_PERMS, &avd);
rcu_read_unlock();
rc2 = avc_xperms_audit(ssid, tsid, tclass, requested,
&avd, xpd, xperm, rc, ad);
if (rc2)
return rc2;
return rc;
}
/**
* avc_has_perm_noaudit - Check permissions but perform no auditing.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @requested: requested permissions, interpreted based on @tclass
* @flags: AVC_STRICT or 0
* @avd: access vector decisions
*
* Check the AVC to determine whether the @requested permissions are granted
* for the SID pair (@ssid, @tsid), interpreting the permissions
* based on @tclass, and call the security server on a cache miss to obtain
* a new decision and add it to the cache. Return a copy of the decisions
* in @avd. Return %0 if all @requested permissions are granted,
* -%EACCES if any permissions are denied, or another -errno upon
* other errors. This function is typically called by avc_has_perm(),
* but may also be called directly to separate permission checking from
* auditing, e.g. in cases where a lock must be held for the check but
* should be released for the auditing.
*/
inline int avc_has_perm_noaudit(u32 ssid, u32 tsid,
u16 tclass, u32 requested,
unsigned flags,
struct av_decision *avd)
{
struct avc_node *node;
struct avc_xperms_node xp_node;
int rc = 0;
u32 denied;
BUG_ON(!requested);
rcu_read_lock();
node = avc_lookup(ssid, tsid, tclass);
if (unlikely(!node))
node = avc_compute_av(ssid, tsid, tclass, avd, &xp_node);
else
memcpy(avd, &node->ae.avd, sizeof(*avd));
denied = requested & ~(avd->allowed);
if (unlikely(denied))
rc = avc_denied(ssid, tsid, tclass, requested, 0, 0, flags, avd);
rcu_read_unlock();
return rc;
}
/**
* avc_has_perm - Check permissions and perform any appropriate auditing.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @requested: requested permissions, interpreted based on @tclass
* @auditdata: auxiliary audit data
* @flags: VFS walk flags
*
* Check the AVC to determine whether the @requested permissions are granted
* for the SID pair (@ssid, @tsid), interpreting the permissions
* based on @tclass, and call the security server on a cache miss to obtain
* a new decision and add it to the cache. Audit the granting or denial of
* permissions in accordance with the policy. Return %0 if all @requested
* permissions are granted, -%EACCES if any permissions are denied, or
* another -errno upon other errors.
*/
int avc_has_perm_flags(u32 ssid, u32 tsid, u16 tclass,
u32 requested, struct common_audit_data *auditdata,
unsigned flags)
{
struct av_decision avd;
int rc, rc2;
rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
rc2 = avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata,
flags);
if (rc2)
return rc2;
return rc;
}
u32 avc_policy_seqno(void)
{
return avc_cache.latest_notif;
}
void avc_disable(void)
{
/*
* If you are looking at this because you have realized that we are
* not destroying the avc_node_cachep it might be easy to fix, but
* I don't know the memory barrier semantics well enough to know. It's
* possible that some other task dereferenced security_ops when
* it still pointed to selinux operations. If that is the case it's
* possible that it is about to use the avc and is about to need the
* avc_node_cachep. I know I could wrap the security.c security_ops call
* in an rcu_lock, but seriously, it's not worth it. Instead I just flush
* the cache and get that memory back.
*/
if (avc_node_cachep) {
avc_flush();
/* kmem_cache_destroy(avc_node_cachep); */
}
}