[PATCH v2 5/5] selinux: Switch locking to RCU.

From: peter.enderborg
Date: Fri Jan 26 2018 - 09:33:43 EST

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From: Peter Enderborg <peter.enderborg@xxxxxxxx>

This patch switch to using RCU locks instead of rwlocks. This has
the big advantage that it does not has preempt disable.

Signed-off-by: Peter Enderborg <peter.enderborg@xxxxxxxx>
Reported-by: BjÃrn Davidsson <bjorn.davidsson@xxxxxxxx>
---
security/selinux/ss/services.c | 162 +++++++++++++++++++++--------------------
1 file changed, 82 insertions(+), 80 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 81c5717..f142ef8 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -87,7 +87,7 @@ int selinux_policycap_alwaysnetwork;
int selinux_policycap_cgroupseclabel;
int selinux_policycap_nnp_nosuid_transition;

-static DEFINE_RWLOCK(policy_rwlock);
+static DEFINE_SPINLOCK(policy_w_lock);

int ss_initialized;

@@ -115,14 +115,14 @@ struct selinux_mapping {
u32 perms[sizeof(u32) * 8];
};

-struct shared_current_mapping {
+struct shared_rcu_mapping {
struct selinux_mapping *current_mapping;
u16 current_mapping_size;
struct policydb policydb;
struct sidtab sidtab;
};

-static struct shared_current_mapping *crm;
+static struct shared_rcu_mapping *crm;

static int selinux_set_mapping(struct policydb *pol,
struct security_class_mapping *map,
@@ -791,7 +791,7 @@ static int security_compute_validatetrans(u32 oldsid, u32 newsid, u32 tasksid,
if (!ss_initialized)
return 0;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

if (!user)
tclass = unmap_class(orig_tclass);
@@ -845,7 +845,7 @@ static int security_compute_validatetrans(u32 oldsid, u32 newsid, u32 tasksid,
}

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -879,7 +879,7 @@ int security_bounded_transition(u32 old_sid, u32 new_sid)
int index;
int rc;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
old_context = sidtab_search(&crm->sidtab, old_sid);
@@ -941,7 +941,7 @@ int security_bounded_transition(u32 old_sid, u32 new_sid)
kfree(old_name);
}
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();

return rc;
}
@@ -1029,7 +1029,7 @@ void security_compute_xperms_decision(u32 ssid,
memset(xpermd->auditallow->p, 0, sizeof(xpermd->auditallow->p));
memset(xpermd->dontaudit->p, 0, sizeof(xpermd->dontaudit->p));

- read_lock(&policy_rwlock);
+ rcu_read_lock();
if (!ss_initialized)
goto allow;

@@ -1083,7 +1083,7 @@ void security_compute_xperms_decision(u32 ssid,
}
}
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return;
allow:
memset(xpermd->allowed->p, 0xff, sizeof(xpermd->allowed->p));
@@ -1110,7 +1110,7 @@ void security_compute_av(u32 ssid,
u16 tclass;
struct context *scontext = NULL, *tcontext = NULL;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
avd_init(avd);
xperms->len = 0;
if (!ss_initialized)
@@ -1143,7 +1143,7 @@ void security_compute_av(u32 ssid,
context_struct_compute_av(scontext, tcontext, tclass, avd, xperms);
map_decision(orig_tclass, avd, crm->policydb.allow_unknown);
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return;
allow:
avd->allowed = 0xffffffff;
@@ -1157,7 +1157,7 @@ void security_compute_av_user(u32 ssid,
{
struct context *scontext = NULL, *tcontext = NULL;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
avd_init(avd);
if (!ss_initialized)
goto allow;
@@ -1188,7 +1188,7 @@ void security_compute_av_user(u32 ssid,

context_struct_compute_av(scontext, tcontext, tclass, avd, NULL);
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return;
allow:
avd->allowed = 0xffffffff;
@@ -1293,7 +1293,7 @@ static int security_sid_to_context_core(u32 sid, char **scontext,
rc = -EINVAL;
goto out;
}
- read_lock(&policy_rwlock);
+ rcu_read_lock();
if (force)
context = sidtab_search_force(&crm->sidtab, sid);
else
@@ -1306,7 +1306,7 @@ static int security_sid_to_context_core(u32 sid, char **scontext,
}
rc = context_struct_to_string(context, scontext, scontext_len);
out_unlock:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
out:
return rc;

@@ -1458,7 +1458,7 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len,
goto out;
}

- read_lock(&policy_rwlock);
+ rcu_read_lock();
rc = string_to_context_struct(&crm->policydb, &crm->sidtab, scontext2,
scontext_len, &context, def_sid);
if (rc == -EINVAL && force) {
@@ -1470,7 +1470,7 @@ static int security_context_to_sid_core(const char *scontext, u32 scontext_len,
rc = sidtab_context_to_sid(&crm->sidtab, &context, sid);
context_destroy(&context);
out_unlock:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
out:
kfree(scontext2);
kfree(str);
@@ -1620,7 +1620,7 @@ static int security_compute_sid(u32 ssid,

context_init(&newcontext);

- read_lock(&policy_rwlock);
+ rcu_read_lock();

if (kern) {
tclass = unmap_class(orig_tclass);
@@ -1759,7 +1759,7 @@ static int security_compute_sid(u32 ssid,
/* Obtain the sid for the context. */
rc = sidtab_context_to_sid(&crm->sidtab, &newcontext, out_sid);
out_unlock:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
context_destroy(&newcontext);
out:
return rc;
@@ -2051,7 +2051,6 @@ static void security_load_policycaps(struct policydb *pdb)
}

static int security_preserve_bools(struct policydb *p);
-
/**
* security_load_policy - Load a security policy configuration.
* @data: binary policy data
@@ -2068,17 +2067,17 @@ int security_load_policy(void *data, size_t len)
struct sidtab oldsidtab, newsidtab;
struct selinux_mapping *oldmap = NULL, *map = NULL;
struct convert_context_args args;
- struct shared_current_mapping *next_rcu;
- struct shared_current_mapping *old_rcu;
+ struct shared_rcu_mapping *next_rcu;
+ struct shared_rcu_mapping *old_rcu;
u32 seqno;
u16 map_size;
int rc = 0;
struct policy_file file = { data, len }, *fp = &file;

if (!ss_initialized) {
- struct shared_current_mapping *first_mapping;
+ struct shared_rcu_mapping *first_mapping;

- first_mapping = kzalloc(sizeof(struct shared_current_mapping),
+ first_mapping = kzalloc(sizeof(struct shared_rcu_mapping),
GFP_KERNEL);
if (!first_mapping) {
rc = -ENOMEM;
@@ -2145,7 +2144,7 @@ int security_load_policy(void *data, size_t len)
goto out;
}

- next_rcu = kzalloc(sizeof(struct shared_current_mapping), GFP_KERNEL);
+ next_rcu = kzalloc(sizeof(struct shared_rcu_mapping), GFP_KERNEL);
if (!next_rcu) {
kfree(oldpolicydb);
rc = -ENOMEM;
@@ -2157,7 +2156,7 @@ int security_load_policy(void *data, size_t len)
goto out;

next_rcu->policydb.len = len;
- read_lock(&policy_rwlock);
+ rcu_read_lock();
/* If switching between different policy types, log MLS status */
if (crm->policydb.mls_enabled && !next_rcu->policydb.mls_enabled)
printk(KERN_INFO "SELinux: Disabling MLS support...\n");
@@ -2210,19 +2209,19 @@ 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);
sidtab_set(&next_rcu->sidtab, &newsidtab);
security_load_policycaps(&next_rcu->policydb);
oldmap = crm->current_mapping;
+ rcu_read_unlock();
next_rcu->current_mapping = map;
next_rcu->current_mapping_size = map_size;

+ spin_lock(&policy_w_lock);
seqno = ++latest_granting;
old_rcu = crm;
crm = next_rcu;
- write_unlock_irq(&policy_rwlock);
-
+ spin_unlock(&policy_w_lock);
+ synchronize_rcu();
/* Free the old policydb and SID table. */
policydb_destroy(oldpolicydb);
sidtab_destroy(&oldsidtab);
@@ -2250,9 +2249,9 @@ size_t security_policydb_len(void)
{
size_t len;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
len = crm->policydb.len;
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();

return len;
}
@@ -2268,7 +2267,7 @@ int security_port_sid(u8 protocol, u16 port, u32 *out_sid)
struct ocontext *c;
int rc = 0;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

c = crm->policydb.ocontexts[OCON_PORT];
while (c) {
@@ -2293,7 +2292,7 @@ int security_port_sid(u8 protocol, u16 port, u32 *out_sid)
}

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2308,7 +2307,7 @@ int security_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *out_sid)
struct ocontext *c;
int rc = 0;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

c = crm->policydb.ocontexts[OCON_IBPKEY];
while (c) {
@@ -2333,7 +2332,7 @@ int security_ib_pkey_sid(u64 subnet_prefix, u16 pkey_num, u32 *out_sid)
*out_sid = SECINITSID_UNLABELED;

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2348,7 +2347,7 @@ int security_ib_endport_sid(const char *dev_name, u8 port_num, u32 *out_sid)
struct ocontext *c;
int rc = 0;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

c = crm->policydb.ocontexts[OCON_IBENDPORT];
while (c) {
@@ -2374,7 +2373,7 @@ int security_ib_endport_sid(const char *dev_name, u8 port_num, u32 *out_sid)
*out_sid = SECINITSID_UNLABELED;

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2388,7 +2387,7 @@ int security_netif_sid(char *name, u32 *if_sid)
int rc = 0;
struct ocontext *c;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

c = crm->policydb.ocontexts[OCON_NETIF];
while (c) {
@@ -2415,7 +2414,7 @@ int security_netif_sid(char *name, u32 *if_sid)
*if_sid = SECINITSID_NETIF;

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2447,7 +2446,7 @@ int security_node_sid(u16 domain,
int rc;
struct ocontext *c;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

switch (domain) {
case AF_INET: {
@@ -2502,7 +2501,7 @@ int security_node_sid(u16 domain,

rc = 0;
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2541,7 +2540,7 @@ int security_get_user_sids(u32 fromsid,
if (!ss_initialized)
goto out;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

context_init(&usercon);

@@ -2593,7 +2592,7 @@ int security_get_user_sids(u32 fromsid,
}
rc = 0;
out_unlock:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
if (rc || !mynel) {
kfree(mysids);
goto out;
@@ -2704,9 +2703,9 @@ int security_genfs_sid(const char *fstype,
{
int retval;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
retval = __security_genfs_sid(fstype, path, orig_sclass, sid);
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return retval;
}

@@ -2721,7 +2720,7 @@ int security_fs_use(struct super_block *sb)
struct superblock_security_struct *sbsec = sb->s_security;
const char *fstype = sb->s_type->name;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

c = crm->policydb.ocontexts[OCON_FSUSE];
while (c) {
@@ -2752,7 +2751,7 @@ int security_fs_use(struct super_block *sb)
}

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2760,7 +2759,7 @@ int security_get_bools(int *len, char ***names, int **values)
{
int i, rc;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
*names = NULL;
*values = NULL;

@@ -2790,7 +2789,7 @@ int security_get_bools(int *len, char ***names, int **values)
}
rc = 0;
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
err:
if (*names) {
@@ -2803,13 +2802,14 @@ int security_get_bools(int *len, char ***names, int **values)

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

- next_rcu = kzalloc(sizeof(struct shared_current_mapping), GFP_KERNEL);
- read_lock(&policy_rwlock);
+ next_rcu = kzalloc(sizeof(struct shared_rcu_mapping), GFP_KERNEL);
+ rcu_read_lock();
old_rcu = crm;
memcpy(&next_rcu->policydb, &old_rcu->policydb,
sizeof(struct policydb));
@@ -2842,13 +2842,15 @@ int security_set_bools(int len, int *values)
if (rc)
goto out;
}
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
+
rc = 0;

- write_lock_irq(&policy_rwlock);
+ spin_lock(&policy_w_lock);
seqno = ++latest_granting;
crm = next_rcu;
- write_unlock_irq(&policy_rwlock);
+ spin_unlock(&policy_w_lock);
+ synchronize_rcu();
out:
if (!rc) {
avc_ss_reset(seqno);
@@ -2868,7 +2870,7 @@ int security_get_bool_value(int index)
int rc;
int len;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -EFAULT;
len = crm->policydb.p_bools.nprim;
@@ -2877,7 +2879,7 @@ int security_get_bool_value(int index)

rc = crm->policydb.bool_val_to_struct[index]->state;
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -2933,7 +2935,7 @@ int security_sid_mls_copy(u32 sid, u32 mls_sid, u32 *new_sid)

context_init(&newcon);

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
context1 = sidtab_search(&crm->sidtab, sid);
@@ -2975,7 +2977,7 @@ int security_sid_mls_copy(u32 sid, u32 mls_sid, u32 *new_sid)

rc = sidtab_context_to_sid(&crm->sidtab, &newcon, new_sid);
out_unlock:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
context_destroy(&newcon);
out:
return rc;
@@ -3032,7 +3034,7 @@ int security_net_peersid_resolve(u32 nlbl_sid, u32 nlbl_type,
if (!crm->policydb.mls_enabled)
return 0;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
nlbl_ctx = sidtab_search(&crm->sidtab, nlbl_sid);
@@ -3059,7 +3061,7 @@ int security_net_peersid_resolve(u32 nlbl_sid, u32 nlbl_type,
* expressive */
*peer_sid = xfrm_sid;
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -3080,7 +3082,7 @@ int security_get_classes(char ***classes, int *nclasses)
{
int rc;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -ENOMEM;
*nclasses = crm->policydb.p_classes.nprim;
@@ -3098,7 +3100,7 @@ int security_get_classes(char ***classes, int *nclasses)
}

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -3120,7 +3122,7 @@ int security_get_permissions(char *class, char ***perms, int *nperms)
int rc, i;
struct class_datum *match;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
match = hashtab_search(crm->policydb.p_classes.table, class);
@@ -3149,11 +3151,11 @@ int security_get_permissions(char *class, char ***perms, int *nperms)
goto err;

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;

err:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
for (i = 0; i < *nperms; i++)
kfree((*perms)[i]);
kfree(*perms);
@@ -3184,9 +3186,9 @@ int security_policycap_supported(unsigned int req_cap)
{
int rc;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
rc = ebitmap_get_bit(&crm->policydb.policycaps, req_cap);
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();

return rc;
}
@@ -3250,7 +3252,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)

context_init(&tmprule->au_ctxt);

- read_lock(&policy_rwlock);
+ rcu_read_lock();

tmprule->au_seqno = latest_granting;

@@ -3294,7 +3296,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
}
rc = 0;
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();

if (rc) {
selinux_audit_rule_free(tmprule);
@@ -3344,7 +3346,7 @@ int selinux_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule,
return -ENOENT;
}

- read_lock(&policy_rwlock);
+ rcu_read_lock();

if (rule->au_seqno < latest_granting) {
match = -ESTALE;
@@ -3435,7 +3437,7 @@ int selinux_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule,
}

out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return match;
}

@@ -3521,7 +3523,7 @@ int security_netlbl_secattr_to_sid(struct netlbl_lsm_secattr *secattr,
return 0;
}

- read_lock(&policy_rwlock);
+ rcu_read_lock();

if (secattr->flags & NETLBL_SECATTR_CACHE)
*sid = *(u32 *)secattr->cache->data;
@@ -3558,12 +3560,12 @@ int security_netlbl_secattr_to_sid(struct netlbl_lsm_secattr *secattr,
} else
*sid = SECSID_NULL;

- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return 0;
out_free:
ebitmap_destroy(&ctx_new.range.level[0].cat);
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -3585,7 +3587,7 @@ int security_netlbl_sid_to_secattr(u32 sid, struct netlbl_lsm_secattr *secattr)
if (!ss_initialized)
return 0;

- read_lock(&policy_rwlock);
+ rcu_read_lock();

rc = -ENOENT;
ctx = sidtab_search(&crm->sidtab, sid);
@@ -3604,7 +3606,7 @@ int security_netlbl_sid_to_secattr(u32 sid, struct netlbl_lsm_secattr *secattr)
mls_export_netlbl_lvl(&crm->policydb, ctx, secattr);
rc = mls_export_netlbl_cat(&crm->policydb, ctx, secattr);
out:
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();
return rc;
}
#endif /* CONFIG_NETLABEL */
@@ -3632,9 +3634,9 @@ int security_read_policy(void **data, size_t *len)
fp.data = *data;
fp.len = *len;

- read_lock(&policy_rwlock);
+ rcu_read_lock();
rc = policydb_write(&crm->policydb, &fp);
- read_unlock(&policy_rwlock);
+ rcu_read_unlock();

if (rc)
return rc;
--
2.7.4

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