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authorStephen Smalley <stephen.smalley.work@gmail.com>2020-08-11 22:01:56 +0300
committerPaul Moore <paul@paul-moore.com>2020-08-18 04:00:33 +0300
commitc7c556f1e81bb9e09656ed6650d0c44c84b7c016 (patch)
treef59001467a93880927534c5bb484bfb72d918cdb /security/selinux/ss/avtab.c
parent02a52c5c8c3b8cbad0f12009cde9f36dbefb6972 (diff)
downloadlinux-c7c556f1e81bb9e09656ed6650d0c44c84b7c016.tar.xz
selinux: refactor changing booleans
Refactor the logic for changing SELinux policy booleans in a similar manner to the refactoring of policy load, thereby reducing the size of the critical section when the policy write-lock is held and making it easier to convert the policy rwlock to RCU in the future. Instead of directly modifying the policydb in place, modify a copy and then swap it into place through a single pointer update. Only fully copy the portions of the policydb that are affected by boolean changes to avoid the full cost of a deep policydb copy. Introduce another level of indirection for the sidtab since changing booleans does not require updating the sidtab, unlike policy load. While we are here, create a common helper for notifying other kernel components and userspace of a policy change and call it from both security_set_bools() and selinux_policy_commit(). Based on an old (2004) patch by Kaigai Kohei [1] to convert the policy rwlock to RCU that was deferred at the time since it did not significantly improve performance and introduced complexity. Peter Enderborg later submitted a patch series to convert to RCU [2] that would have made changing booleans a much more expensive operation by requiring a full policydb_write();policydb_read(); sequence to deep copy the entire policydb and also had concerns regarding atomic allocations. This change is now simplified by the earlier work to encapsulate policy state in the selinux_policy struct and to refactor policy load. After this change, the last major obstacle to converting the policy rwlock to RCU is likely the sidtab live convert support. [1] https://lore.kernel.org/selinux/6e2f9128-e191-ebb3-0e87-74bfccb0767f@tycho.nsa.gov/ [2] https://lore.kernel.org/selinux/20180530141104.28569-1-peter.enderborg@sony.com/ Signed-off-by: Stephen Smalley <stephen.smalley.work@gmail.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'security/selinux/ss/avtab.c')
-rw-r--r--security/selinux/ss/avtab.c49
1 files changed, 48 insertions, 1 deletions
diff --git a/security/selinux/ss/avtab.c b/security/selinux/ss/avtab.c
index 01b300a4a882..0172d87e2b9a 100644
--- a/security/selinux/ss/avtab.c
+++ b/security/selinux/ss/avtab.c
@@ -301,7 +301,6 @@ void avtab_destroy(struct avtab *h)
void avtab_init(struct avtab *h)
{
- kvfree(h->htable);
h->htable = NULL;
h->nel = 0;
}
@@ -340,6 +339,54 @@ int avtab_alloc(struct avtab *h, u32 nrules)
return 0;
}
+int avtab_duplicate(struct avtab *new, struct avtab *orig)
+{
+ int i;
+ struct avtab_node *node, *tmp, *tail;
+
+ memset(new, 0, sizeof(*new));
+
+ new->htable = kvcalloc(orig->nslot, sizeof(void *), GFP_KERNEL);
+ if (!new->htable)
+ return -ENOMEM;
+ new->nslot = orig->nslot;
+ new->mask = orig->mask;
+
+ for (i = 0; i < orig->nslot; i++) {
+ tail = NULL;
+ for (node = orig->htable[i]; node; node = node->next) {
+ tmp = kmem_cache_zalloc(avtab_node_cachep, GFP_KERNEL);
+ if (!tmp)
+ goto error;
+ tmp->key = node->key;
+ if (tmp->key.specified & AVTAB_XPERMS) {
+ tmp->datum.u.xperms =
+ kmem_cache_zalloc(avtab_xperms_cachep,
+ GFP_KERNEL);
+ if (!tmp->datum.u.xperms) {
+ kmem_cache_free(avtab_node_cachep, tmp);
+ goto error;
+ }
+ tmp->datum.u.xperms = node->datum.u.xperms;
+ } else
+ tmp->datum.u.data = node->datum.u.data;
+
+ if (tail)
+ tail->next = tmp;
+ else
+ new->htable[i] = tmp;
+
+ tail = tmp;
+ new->nel++;
+ }
+ }
+
+ return 0;
+error:
+ avtab_destroy(new);
+ return -ENOMEM;
+}
+
void avtab_hash_eval(struct avtab *h, char *tag)
{
int i, chain_len, slots_used, max_chain_len;