[PATCH V3 5/5 selinux-next] selinux: Switch to rcu read locks for avc_compute

From: Peter Enderborg
Date: Wed May 30 2018 - 10:22:03 EST

To be able to preempt avc_compute we need preemptible
locks, this patch switch the rwlock reads to rcu_read_lock.

Signed-off-by: Peter Enderborg <peter.enderborg@xxxxxxxx>
---
security/selinux/ss/services.c | 152 +++++++++++++++++++++--------------------
security/selinux/ss/services.h | 2 +-
2 files changed, 79 insertions(+), 75 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 954ebe490516..a9aa863c47a3 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -84,7 +84,7 @@ static struct selinux_ss selinux_ss;

void selinux_ss_init(struct selinux_ss **ss)
{
- rwlock_init(&selinux_ss.policy_rwlock);
+ spin_lock_init(&selinux_ss.policy_lock);
mutex_init(&selinux_ss.status_lock);
selinux_ss.active_set = kzalloc(sizeof(struct selinux_ruleset),
GFP_KERNEL);
@@ -779,7 +779,7 @@ static int security_compute_validatetrans(struct selinux_state *state,
if (!state->initialized)
return 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -837,7 +837,7 @@ static int security_compute_validatetrans(struct selinux_state *state,
}

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

@@ -879,7 +879,7 @@ int security_bounded_transition(struct selinux_state *state,
if (!state->initialized)
return 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -944,7 +944,7 @@ int security_bounded_transition(struct selinux_state *state,
kfree(old_name);
}
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();

return rc;
}
@@ -1035,7 +1035,7 @@ void security_compute_xperms_decision(struct selinux_state *state,
memset(xpermd->auditallow->p, 0, sizeof(xpermd->auditallow->p));
memset(xpermd->dontaudit->p, 0, sizeof(xpermd->dontaudit->p));

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
if (!state->initialized)
goto allow;

@@ -1092,7 +1092,7 @@ void security_compute_xperms_decision(struct selinux_state *state,
}
}
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
return;
allow:
memset(xpermd->allowed->p, 0xff, sizeof(xpermd->allowed->p));
@@ -1122,7 +1122,7 @@ void security_compute_av(struct selinux_state *state,
u16 tclass;
struct context *scontext = NULL, *tcontext = NULL;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
avd_init(state, avd);
xperms->len = 0;
if (!state->initialized)
@@ -1160,7 +1160,7 @@ void security_compute_av(struct selinux_state *state,
map_decision(&state->ss->active_set->map, orig_tclass, avd,
policydb->allow_unknown);
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
return;
allow:
avd->allowed = 0xffffffff;
@@ -1177,7 +1177,7 @@ void security_compute_av_user(struct selinux_state *state,
struct sidtab *sidtab;
struct context *scontext = NULL, *tcontext = NULL;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
avd_init(state, avd);
if (!state->initialized)
goto allow;
@@ -1212,7 +1212,7 @@ void security_compute_av_user(struct selinux_state *state,
context_struct_compute_av(policydb, scontext, tcontext, tclass, avd,
NULL);
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
return;
allow:
avd->allowed = 0xffffffff;
@@ -1319,7 +1319,7 @@ static int security_sid_to_context_core(struct selinux_state *state,
rc = -EINVAL;
goto out;
}
- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
if (force)
@@ -1335,7 +1335,7 @@ static int security_sid_to_context_core(struct selinux_state *state,
rc = context_struct_to_string(policydb, context, scontext,
scontext_len);
out_unlock:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
out:
return rc;

@@ -1491,7 +1491,7 @@ static int security_context_to_sid_core(struct selinux_state *state,
if (!str)
goto out;
}
- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
rc = string_to_context_struct(policydb, sidtab, scontext2,
@@ -1505,7 +1505,7 @@ static int security_context_to_sid_core(struct selinux_state *state,
rc = sidtab_context_to_sid(sidtab, &context, sid);
context_destroy(&context);
out_unlock:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
out:
kfree(scontext2);
kfree(str);
@@ -1666,7 +1666,7 @@ static int security_compute_sid(struct selinux_state *state,

context_init(&newcontext);

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

if (kern) {
tclass = unmap_class(&state->ss->active_set->map, orig_tclass);
@@ -1806,7 +1806,7 @@ static int security_compute_sid(struct selinux_state *state,
/* Obtain the sid for the context. */
rc = sidtab_context_to_sid(sidtab, &newcontext, out_sid);
out_unlock:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
context_destroy(&newcontext);
out:
return rc;
@@ -2166,14 +2166,14 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
if (rc)
goto pdcerr;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
old_set = state->ss->active_set;
rc = policydb_copy(&old_set->policydb, pdc, &storage, size);

/* save seq */
seqno = state->ss->latest_granting;

- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();

policydb_flattened_free(storage);

@@ -2232,16 +2232,18 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
goto maperr;
}

+
next_set->map.mapping = newmap.mapping;
next_set->map.size = newmap.size;

/* Install the new policydb and SID table. */
- write_lock_irq(&state->ss->policy_rwlock);
- if (seqno == state->ss->latest_granting) {
+ spin_lock_irq(&state->ss->policy_lock);
+ if (likely(seqno == state->ss->latest_granting)) {
security_load_policycaps(state, &next_set->policydb);
seqno = ++state->ss->latest_granting;
state->ss->active_set = next_set;
- write_unlock_irq(&state->ss->policy_rwlock);
+ spin_unlock_irq(&state->ss->policy_lock);
+ synchronize_rcu();

avc_ss_reset(state->avc, seqno);
selnl_notify_policyload(seqno);
@@ -2260,7 +2262,7 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len)
rc = 0;
goto out;
} else {
- write_unlock_irq(&state->ss->policy_rwlock);
+ spin_unlock_irq(&state->ss->policy_lock);
rc = -EAGAIN;
}
maperr:
@@ -2285,9 +2287,9 @@ size_t security_policydb_len(struct selinux_state *state)
struct policydb *p = &state->ss->active_set->policydb;
size_t len;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
len = p->len;
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();

return len;
}
@@ -2306,7 +2308,7 @@ int security_port_sid(struct selinux_state *state,
struct ocontext *c;
int rc = 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2334,7 +2336,7 @@ int security_port_sid(struct selinux_state *state,
}

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

@@ -2352,7 +2354,7 @@ int security_ib_pkey_sid(struct selinux_state *state,
struct ocontext *c;
int rc = 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2380,7 +2382,7 @@ int security_ib_pkey_sid(struct selinux_state *state,
*out_sid = SECINITSID_UNLABELED;

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

@@ -2398,7 +2400,7 @@ int security_ib_endport_sid(struct selinux_state *state,
struct ocontext *c;
int rc = 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2427,7 +2429,7 @@ int security_ib_endport_sid(struct selinux_state *state,
*out_sid = SECINITSID_UNLABELED;

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

@@ -2444,7 +2446,7 @@ int security_netif_sid(struct selinux_state *state,
int rc = 0;
struct ocontext *c;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2474,7 +2476,7 @@ int security_netif_sid(struct selinux_state *state,
*if_sid = SECINITSID_NETIF;

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

@@ -2509,7 +2511,7 @@ int security_node_sid(struct selinux_state *state,
int rc;
struct ocontext *c;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2567,7 +2569,7 @@ int security_node_sid(struct selinux_state *state,

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

@@ -2609,7 +2611,7 @@ int security_get_user_sids(struct selinux_state *state,
if (!state->initialized)
goto out;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2663,7 +2665,7 @@ int security_get_user_sids(struct selinux_state *state,
}
rc = 0;
out_unlock:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
if (rc || !mynel) {
kfree(mysids);
goto out;
@@ -2705,7 +2707,7 @@ int security_get_user_sids(struct selinux_state *state,
* cannot support xattr or use a fixed labeling behavior like
* transition SIDs or task SIDs.
*
- * The caller must acquire the policy_rwlock before calling this function.
+ * The caller must acquire the policy_lock before calling this function.
*/
static inline int __security_genfs_sid(struct selinux_state *state,
const char *fstype,
@@ -2767,7 +2769,7 @@ static inline int __security_genfs_sid(struct selinux_state *state,
* @sclass: file security class
* @sid: SID for path
*
- * Acquire policy_rwlock before calling __security_genfs_sid() and release
+ * Acquire policy_lock before calling __security_genfs_sid() and release
* it afterward.
*/
int security_genfs_sid(struct selinux_state *state,
@@ -2778,9 +2780,9 @@ int security_genfs_sid(struct selinux_state *state,
{
int retval;

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

@@ -2797,7 +2799,7 @@ int security_fs_use(struct selinux_state *state, struct super_block *sb)
struct superblock_security_struct *sbsec = sb->s_security;
const char *fstype = sb->s_type->name;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;
sidtab = state->ss->active_set->sidtab;
@@ -2830,7 +2832,7 @@ int security_fs_use(struct selinux_state *state, struct super_block *sb)
}

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

@@ -2847,7 +2849,7 @@ int security_get_bools(struct selinux_state *state,
return 0;
}

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;

@@ -2880,7 +2882,7 @@ int security_get_bools(struct selinux_state *state,
}
rc = 0;
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
return rc;
err:
if (*names) {
@@ -2914,13 +2916,14 @@ int security_set_bools(struct selinux_state *state, int len, int *values)
goto errout;
}

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();
old_set = state->ss->active_set;
seqno = state->ss->latest_granting;
memcpy(next_set, old_set, sizeof(struct selinux_ruleset));
rc = policydb_copy(&old_set->policydb, &next_set->policydb,
&storage, size);
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
+
if (rc)
goto out;

@@ -2956,12 +2959,13 @@ int security_set_bools(struct selinux_state *state, int len, int *values)
rc = 0;
out:
if (!rc) {
- write_lock_irq(&state->ss->policy_rwlock);
+ spin_lock_irq(&state->ss->policy_lock);
if (seqno == state->ss->latest_granting) {
seqno = ++state->ss->latest_granting;
state->ss->active_set = next_set;
rc = 0;
- write_unlock_irq(&state->ss->policy_rwlock);
+ spin_unlock_irq(&state->ss->policy_lock);
+ synchronize_rcu();
avc_ss_reset(state->avc, seqno);
selnl_notify_policyload(seqno);
selinux_status_update_policyload(state, seqno);
@@ -2970,7 +2974,7 @@ int security_set_bools(struct selinux_state *state, int len, int *values)
kfree(old_set);
} else {
rc = -ENOMEM;
- write_unlock_irq(&state->ss->policy_rwlock);
+ spin_unlock_irq(&state->ss->policy_lock);
printk(KERN_ERR "SELinux: %s failed in seqno %d\n",
__func__, rc);
policydb_destroy(&next_set->policydb);
@@ -2994,7 +2998,7 @@ int security_get_bool_value(struct selinux_state *state,
int rc;
int len;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

policydb = &state->ss->active_set->policydb;

@@ -3005,7 +3009,7 @@ int security_get_bool_value(struct selinux_state *state,

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

@@ -3065,7 +3069,7 @@ int security_sid_mls_copy(struct selinux_state *state,

context_init(&newcon);

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
context1 = sidtab_search(sidtab, sid);
@@ -3108,7 +3112,7 @@ int security_sid_mls_copy(struct selinux_state *state,

rc = sidtab_context_to_sid(sidtab, &newcon, new_sid);
out_unlock:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
context_destroy(&newcon);
out:
return rc;
@@ -3170,7 +3174,7 @@ int security_net_peersid_resolve(struct selinux_state *state,
if (!policydb->mls_enabled)
return 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
nlbl_ctx = sidtab_search(sidtab, nlbl_sid);
@@ -3197,7 +3201,7 @@ int security_net_peersid_resolve(struct selinux_state *state,
* expressive */
*peer_sid = xfrm_sid;
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
return rc;
}

@@ -3226,7 +3230,7 @@ int security_get_classes(struct selinux_state *state,
return 0;
}

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

rc = -ENOMEM;
*nclasses = policydb->p_classes.nprim;
@@ -3244,7 +3248,7 @@ int security_get_classes(struct selinux_state *state,
}

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

@@ -3268,7 +3272,7 @@ int security_get_permissions(struct selinux_state *state,
int rc, i;
struct class_datum *match;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

rc = -EINVAL;
match = hashtab_search(policydb->p_classes.table, class);
@@ -3297,11 +3301,11 @@ int security_get_permissions(struct selinux_state *state,
goto err;

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

err:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
for (i = 0; i < *nperms; i++)
kfree((*perms)[i]);
kfree(*perms);
@@ -3334,9 +3338,9 @@ int security_policycap_supported(struct selinux_state *state,
struct policydb *policydb = &state->ss->active_set->policydb;
int rc;

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

return rc;
}
@@ -3402,7 +3406,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)

context_init(&tmprule->au_ctxt);

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

tmprule->au_seqno = state->ss->latest_granting;

@@ -3443,7 +3447,7 @@ int selinux_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
}
rc = 0;
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();

if (rc) {
selinux_audit_rule_free(tmprule);
@@ -3494,7 +3498,7 @@ int selinux_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule,
return -ENOENT;
}

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

if (rule->au_seqno < state->ss->latest_granting) {
match = -ESTALE;
@@ -3585,7 +3589,7 @@ int selinux_audit_rule_match(u32 sid, u32 field, u32 op, void *vrule,
}

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

@@ -3674,7 +3678,7 @@ int security_netlbl_secattr_to_sid(struct selinux_state *state,
return 0;
}

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

if (secattr->flags & NETLBL_SECATTR_CACHE)
*sid = *(u32 *)secattr->cache->data;
@@ -3710,12 +3714,12 @@ int security_netlbl_secattr_to_sid(struct selinux_state *state,
} else
*sid = SECSID_NULL;

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

@@ -3739,7 +3743,7 @@ int security_netlbl_sid_to_secattr(struct selinux_state *state,
if (!state->initialized)
return 0;

- read_lock(&state->ss->policy_rwlock);
+ rcu_read_lock();

rc = -ENOENT;
ctx = sidtab_search(state->ss->active_set->sidtab, sid);
@@ -3757,7 +3761,7 @@ int security_netlbl_sid_to_secattr(struct selinux_state *state,
mls_export_netlbl_lvl(policydb, ctx, secattr);
rc = mls_export_netlbl_cat(policydb, ctx, secattr);
out:
- read_unlock(&state->ss->policy_rwlock);
+ rcu_read_unlock();
return rc;
}
#endif /* CONFIG_NETLABEL */
@@ -3787,9 +3791,9 @@ int security_read_policy(struct selinux_state *state,
fp.data = *data;
fp.len = *len;

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

if (rc)
return rc;
diff --git a/security/selinux/ss/services.h b/security/selinux/ss/services.h
index 9219649c70ed..84cbcf226551 100644
--- a/security/selinux/ss/services.h
+++ b/security/selinux/ss/services.h
@@ -33,7 +33,7 @@ struct selinux_ruleset {
};
struct selinux_ss {
struct selinux_ruleset *active_set; /* rcu pointer */
- rwlock_t policy_rwlock;
+ spinlock_t policy_lock;
u32 latest_granting;
struct page *status_page;
struct mutex status_lock;
--
2.15.1