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OpenCloudOS-Kernel/security/selinux/avc.c

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/*
* 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 <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"
static const struct av_perm_to_string av_perm_to_string[] = {
#define S_(c, v, s) { c, v, s },
#include "av_perm_to_string.h"
#undef S_
};
static const char *class_to_string[] = {
#define S_(s) s,
#include "class_to_string.h"
#undef S_
};
#define TB_(s) static const char * s [] = {
#define TE_(s) };
#define S_(s) s,
#include "common_perm_to_string.h"
#undef TB_
#undef TE_
#undef S_
static const struct av_inherit av_inherit[] = {
#define S_(c, i, b) { c, common_##i##_perm_to_string, b },
#include "av_inherit.h"
#undef S_
};
const struct selinux_class_perm selinux_class_perm = {
av_perm_to_string,
ARRAY_SIZE(av_perm_to_string),
class_to_string,
ARRAY_SIZE(class_to_string),
av_inherit,
ARRAY_SIZE(av_inherit)
};
#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) \
do { \
per_cpu(avc_cache_stats, get_cpu()).field++; \
put_cpu(); \
} while (0)
#else
#define avc_cache_stats_incr(field) do {} while (0)
#endif
struct avc_entry {
u32 ssid;
u32 tsid;
u16 tclass;
struct av_decision avd;
atomic_t used; /* used recently */
};
struct avc_node {
struct avc_entry ae;
struct list_head list;
struct rcu_head rhead;
};
struct avc_cache {
struct list_head slots[AVC_CACHE_SLOTS];
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 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 **common_pts = NULL;
u32 common_base = 0;
int i, i2, perm;
if (av == 0) {
audit_log_format(ab, " null");
return;
}
for (i = 0; i < ARRAY_SIZE(av_inherit); i++) {
if (av_inherit[i].tclass == tclass) {
common_pts = av_inherit[i].common_pts;
common_base = av_inherit[i].common_base;
break;
}
}
audit_log_format(ab, " {");
i = 0;
perm = 1;
while (perm < common_base) {
if (perm & av) {
audit_log_format(ab, " %s", common_pts[i]);
av &= ~perm;
}
i++;
perm <<= 1;
}
while (i < sizeof(av) * 8) {
if (perm & av) {
for (i2 = 0; i2 < ARRAY_SIZE(av_perm_to_string); i2++) {
if ((av_perm_to_string[i2].tclass == tclass) &&
(av_perm_to_string[i2].value == perm))
break;
}
if (i2 < ARRAY_SIZE(av_perm_to_string)) {
audit_log_format(ab, " %s",
av_perm_to_string[i2].name);
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(class_to_string) || !class_to_string[tclass]);
audit_log_format(ab, " tclass=%s", class_to_string[tclass]);
}
/**
* 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_LIST_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);
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;
rcu_read_lock();
slots_used = 0;
max_chain_len = 0;
for (i = 0; i < AVC_CACHE_SLOTS; i++) {
if (!list_empty(&avc_cache.slots[i])) {
slots_used++;
chain_len = 0;
list_for_each_entry_rcu(node, &avc_cache.slots[i], 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);
}
static void avc_node_free(struct rcu_head *rhead)
{
struct avc_node *node = container_of(rhead, struct avc_node, rhead);
kmem_cache_free(avc_node_cachep, node);
avc_cache_stats_incr(frees);
}
static void avc_node_delete(struct avc_node *node)
{
list_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)
{
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)
{
list_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;
for (try = 0, ecx = 0; try < AVC_CACHE_SLOTS; try++ ) {
hvalue = atomic_inc_return(&avc_cache.lru_hint) & (AVC_CACHE_SLOTS - 1);
if (!spin_trylock_irqsave(&avc_cache.slots_lock[hvalue], flags))
continue;
list_for_each_entry(node, &avc_cache.slots[hvalue], list) {
if (atomic_dec_and_test(&node->ae.used)) {
/* Recently Unused */
avc_node_delete(node);
avc_cache_stats_incr(reclaims);
ecx++;
if (ecx >= AVC_CACHE_RECLAIM) {
spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags);
goto out;
}
}
}
spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], 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_RCU_HEAD(&node->rhead);
INIT_LIST_HEAD(&node->list);
atomic_set(&node->ae.used, 1);
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 avc_entry *ae)
{
node->ae.ssid = ssid;
node->ae.tsid = tsid;
node->ae.tclass = tclass;
memcpy(&node->ae.avd, &ae->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;
hvalue = avc_hash(ssid, tsid, tclass);
list_for_each_entry_rcu(node, &avc_cache.slots[hvalue], list) {
if (ssid == node->ae.ssid &&
tclass == node->ae.tclass &&
tsid == node->ae.tsid) {
ret = node;
break;
}
}
if (ret == NULL) {
/* cache miss */
goto out;
}
/* cache hit */
if (atomic_read(&ret->ae.used) != 1)
atomic_set(&ret->ae.used, 1);
out:
return ret;
}
/**
* avc_lookup - Look up an AVC entry.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @requested: requested permissions, interpreted based on @tclass
*
* Look up an AVC entry that is valid for the
* @requested permissions between the SID pair
* (@ssid, @tsid), interpreting the permissions
* based on @tclass. If a valid AVC entry exists,
* then this function return the avc_node.
* Otherwise, this function returns NULL.
*/
static struct avc_node *avc_lookup(u32 ssid, u32 tsid, u16 tclass, u32 requested)
{
struct avc_node *node;
avc_cache_stats_incr(lookups);
node = avc_search_node(ssid, tsid, tclass);
if (node && ((node->ae.avd.decided & requested) == requested)) {
avc_cache_stats_incr(hits);
goto out;
}
node = NULL;
avc_cache_stats_incr(misses);
out:
return node;
}
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(&notif_lock, flag);
if (is_insert) {
if (seqno < avc_cache.latest_notif) {
printk(KERN_WARNING "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(&notif_lock, flag);
return ret;
}
/**
* avc_insert - Insert an AVC entry.
* @ssid: source security identifier
* @tsid: target security identifier
* @tclass: target security class
* @ae: AVC entry
*
* 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 @ae->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 avc_entry *ae)
{
struct avc_node *pos, *node = NULL;
int hvalue;
unsigned long flag;
if (avc_latest_notif_update(ae->avd.seqno, 1))
goto out;
node = avc_alloc_node();
if (node) {
hvalue = avc_hash(ssid, tsid, tclass);
avc_node_populate(node, ssid, tsid, tclass, ae);
spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
list_for_each_entry(pos, &avc_cache.slots[hvalue], list) {
if (pos->ae.ssid == ssid &&
pos->ae.tsid == tsid &&
pos->ae.tclass == tclass) {
avc_node_replace(node, pos);
goto found;
}
}
list_add_rcu(&node->list, &avc_cache.slots[hvalue]);
found:
spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
}
out:
return node;
}
static inline void avc_print_ipv6_addr(struct audit_buffer *ab,
struct in6_addr *addr, __be16 port,
char *name1, char *name2)
{
if (!ipv6_addr_any(addr))
audit_log_format(ab, " %s=" NIP6_FMT, name1, NIP6(*addr));
if (port)
audit_log_format(ab, " %s=%d", name2, ntohs(port));
}
static inline void avc_print_ipv4_addr(struct audit_buffer *ab, __be32 addr,
__be16 port, char *name1, char *name2)
{
if (addr)
audit_log_format(ab, " %s=" NIPQUAD_FMT, name1, NIPQUAD(addr));
if (port)
audit_log_format(ab, " %s=%d", name2, ntohs(port));
}
/**
* 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
*
* 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.
*/
void avc_audit(u32 ssid, u32 tsid,
u16 tclass, u32 requested,
struct av_decision *avd, int result, struct avc_audit_data *a)
{
struct task_struct *tsk = current;
struct inode *inode = NULL;
u32 denied, audited;
struct audit_buffer *ab;
denied = requested & ~avd->allowed;
if (denied) {
audited = denied;
if (!(audited & avd->auditdeny))
return;
} else if (result) {
audited = denied = requested;
} else {
audited = requested;
if (!(audited & avd->auditallow))
return;
}
ab = audit_log_start(current->audit_context, GFP_ATOMIC, AUDIT_AVC);
if (!ab)
return; /* audit_panic has been called */
audit_log_format(ab, "avc: %s ", denied ? "denied" : "granted");
avc_dump_av(ab, tclass,audited);
audit_log_format(ab, " for ");
if (a && a->tsk)
tsk = a->tsk;
if (tsk && tsk->pid) {
audit_log_format(ab, " pid=%d comm=", tsk->pid);
audit_log_untrustedstring(ab, tsk->comm);
}
if (a) {
switch (a->type) {
case AVC_AUDIT_DATA_IPC:
audit_log_format(ab, " key=%d", a->u.ipc_id);
break;
case AVC_AUDIT_DATA_CAP:
audit_log_format(ab, " capability=%d", a->u.cap);
break;
case AVC_AUDIT_DATA_FS:
if (a->u.fs.dentry) {
struct dentry *dentry = a->u.fs.dentry;
if (a->u.fs.mnt) {
audit_log_d_path(ab, "path=", dentry, a->u.fs.mnt);
} else {
audit_log_format(ab, " name=");
audit_log_untrustedstring(ab, dentry->d_name.name);
}
inode = dentry->d_inode;
} else if (a->u.fs.inode) {
struct dentry *dentry;
inode = a->u.fs.inode;
dentry = d_find_alias(inode);
if (dentry) {
audit_log_format(ab, " name=");
audit_log_untrustedstring(ab, dentry->d_name.name);
dput(dentry);
}
}
if (inode)
audit_log_format(ab, " dev=%s ino=%lu",
inode->i_sb->s_id,
inode->i_ino);
break;
case AVC_AUDIT_DATA_NET:
if (a->u.net.sk) {
struct sock *sk = a->u.net.sk;
struct unix_sock *u;
int len = 0;
char *p = NULL;
switch (sk->sk_family) {
case AF_INET: {
struct inet_sock *inet = inet_sk(sk);
avc_print_ipv4_addr(ab, inet->rcv_saddr,
inet->sport,
"laddr", "lport");
avc_print_ipv4_addr(ab, inet->daddr,
inet->dport,
"faddr", "fport");
break;
}
case AF_INET6: {
struct inet_sock *inet = inet_sk(sk);
struct ipv6_pinfo *inet6 = inet6_sk(sk);
avc_print_ipv6_addr(ab, &inet6->rcv_saddr,
inet->sport,
"laddr", "lport");
avc_print_ipv6_addr(ab, &inet6->daddr,
inet->dport,
"faddr", "fport");
break;
}
case AF_UNIX:
u = unix_sk(sk);
if (u->dentry) {
audit_log_d_path(ab, "path=",
u->dentry, u->mnt);
break;
}
if (!u->addr)
break;
len = u->addr->len-sizeof(short);
p = &u->addr->name->sun_path[0];
audit_log_format(ab, " path=");
if (*p)
audit_log_untrustedstring(ab, p);
else
audit_log_hex(ab, p, len);
break;
}
}
switch (a->u.net.family) {
case AF_INET:
avc_print_ipv4_addr(ab, a->u.net.v4info.saddr,
a->u.net.sport,
"saddr", "src");
avc_print_ipv4_addr(ab, a->u.net.v4info.daddr,
a->u.net.dport,
"daddr", "dest");
break;
case AF_INET6:
avc_print_ipv6_addr(ab, &a->u.net.v6info.saddr,
a->u.net.sport,
"saddr", "src");
avc_print_ipv6_addr(ab, &a->u.net.v6info.daddr,
a->u.net.dport,
"daddr", "dest");
break;
}
if (a->u.net.netif)
audit_log_format(ab, " netif=%s",
a->u.net.netif);
break;
}
}
audit_log_format(ab, " ");
avc_dump_query(ab, ssid, tsid, tclass);
audit_log_end(ab);
}
/**
* 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
* 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
*
* 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 update the AVC entry. The original AVC-entry object
* will release later by RCU.
*/
static int avc_update_node(u32 event, u32 perms, u32 ssid, u32 tsid, u16 tclass)
{
int hvalue, rc = 0;
unsigned long flag;
struct avc_node *pos, *node, *orig = NULL;
node = avc_alloc_node();
if (!node) {
rc = -ENOMEM;
goto out;
}
/* Lock the target slot */
hvalue = avc_hash(ssid, tsid, tclass);
spin_lock_irqsave(&avc_cache.slots_lock[hvalue], flag);
list_for_each_entry(pos, &avc_cache.slots[hvalue], list){
if ( ssid==pos->ae.ssid &&
tsid==pos->ae.tsid &&
tclass==pos->ae.tclass ){
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);
switch (event) {
case AVC_CALLBACK_GRANT:
node->ae.avd.allowed |= perms;
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;
}
avc_node_replace(node, orig);
out_unlock:
spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flag);
out:
return rc;
}
/**
* 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 i, rc = 0, tmprc;
unsigned long flag;
struct avc_node *node;
for (i = 0; i < AVC_CACHE_SLOTS; i++) {
spin_lock_irqsave(&avc_cache.slots_lock[i], flag);
list_for_each_entry(node, &avc_cache.slots[i], list)
avc_node_delete(node);
spin_unlock_irqrestore(&avc_cache.slots_lock[i], flag);
}
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;
}
/**
* 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.
*/
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_entry entry, *p_ae;
int rc = 0;
u32 denied;
rcu_read_lock();
node = avc_lookup(ssid, tsid, tclass, requested);
if (!node) {
rcu_read_unlock();
rc = security_compute_av(ssid,tsid,tclass,requested,&entry.avd);
if (rc)
goto out;
rcu_read_lock();
node = avc_insert(ssid,tsid,tclass,&entry);
}
p_ae = node ? &node->ae : &entry;
if (avd)
memcpy(avd, &p_ae->avd, sizeof(*avd));
denied = requested & ~(p_ae->avd.allowed);
if (!requested || denied) {
if (selinux_enforcing || (flags & AVC_STRICT))
rc = -EACCES;
else
if (node)
avc_update_node(AVC_CALLBACK_GRANT,requested,
ssid,tsid,tclass);
}
rcu_read_unlock();
out:
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
*
* 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(u32 ssid, u32 tsid, u16 tclass,
u32 requested, struct avc_audit_data *auditdata)
{
struct av_decision avd;
int rc;
rc = avc_has_perm_noaudit(ssid, tsid, tclass, requested, 0, &avd);
avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
return rc;
}
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