uci: fix atomicity of uci_add_list

The function uci_add_list is not atomic, when an alloc inside
uci_add_element_list fails the option can be left in an indeterminate
state.

Refactor uci_add_list to fix this and make the code flow easier to
read.

Signed-off-by: Jan Venekamp <jan@venekamp.net>

diff --git a/list.c b/list.c
index ba099b646bc1a8c646490a25c08104cd9667c808..3518967c668ee2c9b0234d705f776230e459bbc9 100644 (file)
--- a/list.c
+++ b/list.c
@@ -497,19 +497,6 @@ uci_expand_ptr(struct uci_context *ctx, struct uci_ptr *ptr, bool complete)
                return NULL;
 }
 
-static void uci_add_element_list(struct uci_context *ctx, struct uci_ptr *ptr, bool internal)
-{
-       struct uci_element *e;
-       struct uci_package *p;
-
-       p = ptr->p;
-       if (!internal && p->has_delta)
-               uci_add_delta(ctx, &p->delta, UCI_CMD_LIST_ADD, ptr->section, ptr->option, ptr->value);
-
-       e = uci_alloc_generic(ctx, UCI_TYPE_ITEM, ptr->value, sizeof(struct uci_option));
-       uci_list_add(&ptr->o->v.list, &e->list);
-}
-
 int uci_rename(struct uci_context *ctx, struct uci_ptr *ptr)
 {
        /* NB: UCI_INTERNAL use means without delta tracking */
@@ -623,8 +610,7 @@ int uci_add_list(struct uci_context *ctx, struct uci_ptr *ptr)
 {
        /* NB: UCI_INTERNAL use means without delta tracking */
        bool internal = ctx && ctx->internal;
-       struct uci_option *volatile prev = NULL;
-       const char *volatile value2 = NULL;
+       struct uci_element *volatile e1 = NULL, *volatile e2 = NULL;
 
        UCI_HANDLE_ERR(ctx);
 
@@ -632,34 +618,48 @@ int uci_add_list(struct uci_context *ctx, struct uci_ptr *ptr)
        UCI_ASSERT(ctx, ptr->s);
        UCI_ASSERT(ctx, ptr->value);
 
-       if (ptr->o) {
-               switch (ptr->o->type) {
-               case UCI_TYPE_STRING:
-                       /* we already have a string value, convert that to a list */
-                       prev = ptr->o;
-                       value2 = ptr->value;
-                       ptr->value = ptr->o->v.string;
-                       break;
-               case UCI_TYPE_LIST:
-                       uci_add_element_list(ctx, ptr, internal);
-                       return 0;
-               default:
-                       UCI_THROW(ctx, UCI_ERR_INVAL);
-                       break;
-               }
+       if (ptr->o && ptr->o->type != UCI_TYPE_LIST && ptr->o->type != UCI_TYPE_STRING) {
+               UCI_THROW(ctx, UCI_ERR_INVAL);
        }
 
-       ptr->o = uci_alloc_list(ptr->s, ptr->option);
-       if (prev) {
-               uci_add_element_list(ctx, ptr, true);
-               if (ptr->option == prev->e.name)
+       /* create new item */
+       e1 = uci_alloc_generic(ctx, UCI_TYPE_ITEM, ptr->value, sizeof(struct uci_option));
+
+       if (!ptr->o) {
+               /* create new list */
+               UCI_TRAP_SAVE(ctx, error);
+               ptr->o = uci_alloc_list(ptr->s, ptr->option);
+               UCI_TRAP_RESTORE(ctx);
+               ptr->last = &ptr->o->e;
+       } else if (ptr->o->type == UCI_TYPE_STRING) {
+               /* create new list and add old string value as item to list */
+               struct uci_option *old = ptr->o;
+               UCI_TRAP_SAVE(ctx, error);
+               e2 = uci_alloc_generic(ctx, UCI_TYPE_ITEM, old->v.string, sizeof(struct uci_option));
+               ptr->o = uci_alloc_list(ptr->s, ptr->option);
+               UCI_TRAP_RESTORE(ctx);
+               uci_list_add(&ptr->o->v.list, &e2->list);
+
+               /* remove old option */
+               if (ptr->option == old->e.name)
                        ptr->option = ptr->o->e.name;
-               uci_free_option(prev);
-               ptr->value = value2;
+               uci_free_option(old);
+               ptr->last = &ptr->o->e;
        }
-       uci_add_element_list(ctx, ptr, internal);
+
+       /* add new item to list */
+       uci_list_add(&ptr->o->v.list, &e1->list);
+
+       if (!internal && ptr->p->has_delta)
+               uci_add_delta(ctx, &ptr->p->delta, UCI_CMD_LIST_ADD, ptr->section, ptr->option, ptr->value);
 
        return 0;
+error:
+       if (e1 != NULL)
+               uci_free_element(e1);
+       if (e2 != NULL)
+               uci_free_element(e2);
+       UCI_THROW(ctx, ctx->err);
 }
 
 int uci_del_list(struct uci_context *ctx, struct uci_ptr *ptr)