Fix unsafe uses of ast_context pointers.

Although ast_context_find, ast_context_find_or_create and
ast_context_destroy perform locking of the contexts table,
any context pointer can become invalid at any time that the
contexts table is unlocked. This change adds locking around
all complete operations involving these functions.

Places where ast_context_find was followed by ast_context_destroy
have been replaced with calls ast_context_destroy_by_name.

ASTERISK-25094 #close
Reported by: Corey Farrell

Change-Id: I1866b6787730c9c4f3f836b6133ffe9c820734fa

1 files changed, 30 insertions, 6 deletions

diff --git a/main/pbx.c b/main/pbx.c
index 45909f5d9..0da0fef1e 100644
--- a/main/pbx.c
+++ b/main/pbx.c
@@ -8739,9 +8739,9 @@ struct ast_context *ast_context_find_or_create(struct ast_context **extcontexts,
 		ast_rdlock_contexts();
 		local_contexts = &contexts;
 		tmp = ast_hashtab_lookup(contexts_table, &search);
-		ast_unlock_contexts();
 		if (tmp) {
 			tmp->refcount++;
+			ast_unlock_contexts();
 			return tmp;
 		}
 	} else { /* local contexts just in a linked list; search there for the new context; slow, linear search, but not frequent */
@@ -8765,11 +8765,13 @@ struct ast_context *ast_context_find_or_create(struct ast_context **extcontexts,
 		tmp->refcount = 1;
 	} else {
 		ast_log(LOG_ERROR, "Danger! We failed to allocate a context for %s!\n", name);
+		if (!extcontexts) {
+			ast_unlock_contexts();
+		}
 		return NULL;
 	}
 
 	if (!extcontexts) {
-		ast_wrlock_contexts();
 		tmp->next = *local_contexts;
 		*local_contexts = tmp;
 		ast_hashtab_insert_safe(contexts_table, tmp); /*put this context into the tree */
@@ -9668,18 +9670,24 @@ int ast_context_add_ignorepat2(struct ast_context *con, const char *value, const
 
 int ast_ignore_pattern(const char *context, const char *pattern)
 {
-	struct ast_context *con = ast_context_find(context);
+	int ret = 0;
+	struct ast_context *con;
 
+	ast_rdlock_contexts();
+	con = ast_context_find(context);
 	if (con) {
 		struct ast_ignorepat *pat;
 
 		for (pat = con->ignorepats; pat; pat = pat->next) {
-			if (ast_extension_match(pat->pattern, pattern))
-				return 1;
+			if (ast_extension_match(pat->pattern, pattern)) {
+				ret = 1;
+				break;
+			}
 		}
 	}
+	ast_unlock_contexts();
 
-	return 0;
+	return ret;
 }
 
 /*
@@ -10887,6 +10895,22 @@ void __ast_context_destroy(struct ast_context *list, struct ast_hashtab *context
 	}
 }
 
+int ast_context_destroy_by_name(const char *context, const char *registrar)
+{
+	struct ast_context *con;
+	int ret = -1;
+
+	ast_wrlock_contexts();
+	con = ast_context_find(context);
+	if (con) {
+		ast_context_destroy(con, registrar);
+		ret = 0;
+	}
+	ast_unlock_contexts();
+
+	return ret;
+}
+
 void ast_context_destroy(struct ast_context *con, const char *registrar)
 {
 	ast_wrlock_contexts();