[PATCH v2 4/5] selinux: Use pointer to switch policydb and sidtab

From: peter.enderborg
Date: Fri Jan 26 2018 - 09:33:33 EST

Next message: peter.enderborg: "[PATCH v2 5/5] selinux: Switch locking to RCU."
Previous message: peter.enderborg: "[PATCH v2 3/5] selinux: Move sidtab to pointer structure"
In reply to: peter.enderborg: "[PATCH v2 3/5] selinux: Move sidtab to pointer structure"
Next in thread: Stephen Smalley: "Re: [PATCH v2 4/5] selinux: Use pointer to switch policydb and sidtab"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

From: Peter Enderborg <peter.enderborg@xxxxxxxx>

This i preparation for switching to RCU locks. To be able to use
RCU we need atomic switched pointer. This adds the dynamic
memory copying to be a single pointer. It copy all the
data structures in to new ones. This is an overhead
for writing rules but the benifit is RCU.

Signed-off-by: Peter Enderborg <peter.enderborg@xxxxxxxx>
---
security/selinux/ss/services.c | 139 +++++++++++++++++++++++------------------
1 file changed, 78 insertions(+), 61 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 2a8486c..81c5717 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2064,76 +2064,67 @@ static int security_preserve_bools(struct policydb *p);
*/
int security_load_policy(void *data, size_t len)
{
- struct policydb *oldpolicydb, *newpolicydb;
+ struct policydb *oldpolicydb;
struct sidtab oldsidtab, newsidtab;
struct selinux_mapping *oldmap = NULL, *map = NULL;
struct convert_context_args args;
- struct shared_current_mapping *new_mapping;
struct shared_current_mapping *next_rcu;
-
+ struct shared_current_mapping *old_rcu;
u32 seqno;
u16 map_size;
int rc = 0;
struct policy_file file = { data, len }, *fp = &file;

- oldpolicydb = kzalloc(2 * sizeof(*oldpolicydb), GFP_KERNEL);
- if (!oldpolicydb) {
- rc = -ENOMEM;
- goto out;
- }
- new_mapping = kzalloc(sizeof(struct shared_current_mapping),
- GFP_KERNEL);
- if (!new_mapping) {
- rc = -ENOMEM;
- goto out;
- }
- newpolicydb = oldpolicydb + 1;
- next_rcu = kmalloc(sizeof(struct shared_current_mapping), GFP_KERNEL);
- if (!next_rcu) {
- rc = -ENOMEM;
- goto out;
- }
-
if (!ss_initialized) {
- crm = kzalloc(sizeof(struct shared_current_mapping),
- GFP_KERNEL);
- if (!crm) {
+ struct shared_current_mapping *first_mapping;
+
+ first_mapping = kzalloc(sizeof(struct shared_current_mapping),
+ GFP_KERNEL);
+ if (!first_mapping) {
rc = -ENOMEM;
goto out;
}
avtab_cache_init();
ebitmap_cache_init();
hashtab_cache_init();
- rc = policydb_read(&crm->policydb, fp);
+ rc = policydb_read(&first_mapping->policydb, fp);
if (rc) {
avtab_cache_destroy();
ebitmap_cache_destroy();
hashtab_cache_destroy();
+ kfree(first_mapping);
goto out;
}

- crm->policydb.len = len;
- rc = selinux_set_mapping(&crm->policydb, secclass_map,
- &crm->current_mapping,
- &crm->current_mapping_size);
+ first_mapping->policydb.len = len;
+ rc = selinux_set_mapping(&first_mapping->policydb, secclass_map,
+ &first_mapping->current_mapping,
+ &first_mapping->current_mapping_size);
if (rc) {
- policydb_destroy(&crm->policydb);
+ policydb_destroy(&first_mapping->policydb);
avtab_cache_destroy();
ebitmap_cache_destroy();
hashtab_cache_destroy();
+ kfree(first_mapping);
goto out;
}

- rc = policydb_load_isids(&crm->policydb, &crm->sidtab);
+ rc = policydb_load_isids(&first_mapping->policydb,
+ &first_mapping->sidtab);
if (rc) {
- policydb_destroy(&crm->policydb);
+ policydb_destroy(&first_mapping->policydb);
avtab_cache_destroy();
ebitmap_cache_destroy();
hashtab_cache_destroy();
+ kfree(first_mapping);
goto out;
}

- security_load_policycaps(&crm->policydb);
+ security_load_policycaps(&first_mapping->policydb);
+ crm = first_mapping;
+
+ smp_mb(); /* make sure that crm exist before we */
+ /* switch ss_initialized */
ss_initialized = 1;
seqno = ++latest_granting;
selinux_complete_init();
@@ -2148,30 +2139,44 @@ int security_load_policy(void *data, size_t len)
#if 0
sidtab_hash_eval(&crm->sidtab, "sids");
#endif
+ oldpolicydb = kzalloc(sizeof(*oldpolicydb), GFP_KERNEL);
+ if (!oldpolicydb) {
+ rc = -ENOMEM;
+ goto out;
+ }
+
+ next_rcu = kzalloc(sizeof(struct shared_current_mapping), GFP_KERNEL);
+ if (!next_rcu) {
+ kfree(oldpolicydb);
+ rc = -ENOMEM;
+ goto out;
+ }

- rc = policydb_read(newpolicydb, fp);
+ rc = policydb_read(&next_rcu->policydb, fp);
if (rc)
goto out;

- newpolicydb->len = len;
+ next_rcu->policydb.len = len;
+ read_lock(&policy_rwlock);
/* If switching between different policy types, log MLS status */
- if (crm->policydb.mls_enabled && !newpolicydb->mls_enabled)
+ if (crm->policydb.mls_enabled && !next_rcu->policydb.mls_enabled)
printk(KERN_INFO "SELinux: Disabling MLS support...\n");
- else if (!crm->policydb.mls_enabled && newpolicydb->mls_enabled)
+ else if (!crm->policydb.mls_enabled && next_rcu->policydb.mls_enabled)
printk(KERN_INFO "SELinux: Enabling MLS support...\n");

- rc = policydb_load_isids(newpolicydb, &newsidtab);
+ rc = policydb_load_isids(&next_rcu->policydb, &newsidtab);
if (rc) {
printk(KERN_ERR "SELinux: unable to load the initial SIDs\n");
- policydb_destroy(newpolicydb);
+ policydb_destroy(&next_rcu->policydb);
goto out;
}

- rc = selinux_set_mapping(newpolicydb, secclass_map, &map, &map_size);
+ rc = selinux_set_mapping(&next_rcu->policydb, secclass_map,
+ &map, &map_size);
if (rc)
goto err;

- rc = security_preserve_bools(newpolicydb);
+ rc = security_preserve_bools(&next_rcu->policydb);
if (rc) {
printk(KERN_ERR "SELinux: unable to preserve booleans\n");
goto err;
@@ -2189,7 +2194,7 @@ int security_load_policy(void *data, size_t len)
* in the new SID table.
*/
args.oldp = &crm->policydb;
- args.newp = newpolicydb;
+ args.newp = &next_rcu->policydb;
rc = sidtab_map(&newsidtab, convert_context, &args);
if (rc) {
printk(KERN_ERR "SELinux: unable to convert the internal"
@@ -2204,8 +2209,9 @@ int security_load_policy(void *data, size_t len)

/* Install the new policydb and SID table. */
/* next */
+ security_load_policycaps(&next_rcu->policydb);
+ read_unlock(&policy_rwlock);
write_lock_irq(&policy_rwlock);
- memcpy(&next_rcu->policydb, newpolicydb, sizeof(struct policydb));
sidtab_set(&next_rcu->sidtab, &newsidtab);
security_load_policycaps(&next_rcu->policydb);
oldmap = crm->current_mapping;
@@ -2213,8 +2219,9 @@ int security_load_policy(void *data, size_t len)
next_rcu->current_mapping_size = map_size;

seqno = ++latest_granting;
- write_unlock_irq(&policy_rwlock);
+ old_rcu = crm;
crm = next_rcu;
+ write_unlock_irq(&policy_rwlock);

/* Free the old policydb and SID table. */
policydb_destroy(oldpolicydb);
@@ -2226,17 +2233,16 @@ int security_load_policy(void *data, size_t len)
selinux_status_update_policyload(seqno);
selinux_netlbl_cache_invalidate();
selinux_xfrm_notify_policyload();
+ kfree(oldpolicydb);
+ kfree(old_rcu);

rc = 0;
goto out;
-
err:
kfree(map);
sidtab_destroy(&newsidtab);
- policydb_destroy(newpolicydb);
-
+ policydb_destroy(&next_rcu->policydb);
out:
- kfree(oldpolicydb);
return rc;
}

@@ -2795,54 +2801,65 @@ int security_get_bools(int *len, char ***names, int **values)
goto out;
}

-
int security_set_bools(int len, int *values)
{
+ struct shared_current_mapping *next_rcu, *old_rcu;
int i, rc;
int lenp, seqno = 0;
struct cond_node *cur;

- write_lock_irq(&policy_rwlock);
-
+ next_rcu = kzalloc(sizeof(struct shared_current_mapping), GFP_KERNEL);
+ read_lock(&policy_rwlock);
+ old_rcu = crm;
+ memcpy(&next_rcu->policydb, &old_rcu->policydb,
+ sizeof(struct policydb));
rc = -EFAULT;
- lenp = crm->policydb.p_bools.nprim;
+ lenp = next_rcu->policydb.p_bools.nprim;
+
if (len != lenp)
goto out;

for (i = 0; i < len; i++) {
if (!!values[i] !=
- crm->policydb.bool_val_to_struct[i]->state) {
+ next_rcu->policydb.bool_val_to_struct[i]->state) {
audit_log(current->audit_context, GFP_ATOMIC,
AUDIT_MAC_CONFIG_CHANGE,
"bool=%s val=%d old_val=%d auid=%u ses=%u",
- sym_name(&crm->policydb, SYM_BOOLS, i),
+ sym_name(&next_rcu->policydb, SYM_BOOLS, i),
!!values[i],
- crm->policydb.bool_val_to_struct[i]->state,
+ next_rcu->policydb.bool_val_to_struct[i]->state,
from_kuid(&init_user_ns, audit_get_loginuid(current)),
audit_get_sessionid(current));
}
if (values[i])
- crm->policydb.bool_val_to_struct[i]->state = 1;
+ next_rcu->policydb.bool_val_to_struct[i]->state = 1;
else
- crm->policydb.bool_val_to_struct[i]->state = 0;
+ next_rcu->policydb.bool_val_to_struct[i]->state = 0;
}

- for (cur = crm->policydb.cond_list; cur; cur = cur->next) {
- rc = evaluate_cond_node(&crm->policydb, cur);
+ for (cur = next_rcu->policydb.cond_list; cur; cur = cur->next) {
+ rc = evaluate_cond_node(&next_rcu->policydb, cur);
if (rc)
goto out;
}
+ read_unlock(&policy_rwlock);
+ rc = 0;

+ write_lock_irq(&policy_rwlock);
seqno = ++latest_granting;
- rc = 0;
-out:
+ crm = next_rcu;
write_unlock_irq(&policy_rwlock);
+out:
if (!rc) {
avc_ss_reset(seqno);
selnl_notify_policyload(seqno);
selinux_status_update_policyload(seqno);
selinux_xfrm_notify_policyload();
+ } else {
+ kfree(next_rcu);
}
+ kfree(old_rcu);
+
return rc;
}

--
2.7.4

Next message: peter.enderborg: "[PATCH v2 5/5] selinux: Switch locking to RCU."
Previous message: peter.enderborg: "[PATCH v2 3/5] selinux: Move sidtab to pointer structure"
In reply to: peter.enderborg: "[PATCH v2 3/5] selinux: Move sidtab to pointer structure"
Next in thread: Stephen Smalley: "Re: [PATCH v2 4/5] selinux: Use pointer to switch policydb and sidtab"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]