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linux/security/selinux/avc.c
Stephen Smalley 99f6d61bda [PATCH] selinux: require AUDIT 
Make SELinux depend on AUDIT as it requires the basic audit support to log
permission denials at all.  Note that AUDITSYSCALL remains optional for
SELinux, although it can be useful in providing further information upon
denials.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-07 16:12:33 -08:00

914 lines
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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
{
u16 tclass;
u32 value;
const char *name;
} 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
{
u16 tclass;
const char **common_pts;
u32 common_base;
} av_inherit[] = {
#define S_(c, i, b) { c, common_##i##_perm_to_string, b },
#include "av_inherit.h"
#undef S_
};
#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 kmem_cache_t *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);
}
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, 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_alloc(avc_node_cachep, SLAB_ATOMIC);
if (!node)
goto out;
memset(node, 0, sizeof(*node));
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, u32 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_avc_path(dentry, a->u.fs.mnt);
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=%ld",
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_avc_path(u->dentry, u->mnt);
audit_log_format(ab, " name=");
audit_log_untrustedstring(ab, u->dentry->d_name.name);
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;
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) {
rc = c->callback(AVC_CALLBACK_RESET,
0, 0, 0, 0, NULL);
if (rc)
goto out;
}
}
avc_latest_notif_update(seqno, 0);
out:
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
* @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,
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)
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, &avd);
avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
return rc;
}
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