[PATCH v2 4/4] tools/xenstored: remove permissions related to dead domain

[Juergen Gross <jgross@xxxxxxxx>]

Wit unprivileged domains now capable to use the @releaseDomain watch,
there is no reason not to remove any node permissions which relate to
a domain which has been removed.

This resolves a complex scenario where a new domain could inherit the
permissions of an old one with the same domid.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
---
V2: use priv_domid instead of literal 0 in message (Jason Andryuk)
---
 tools/xenstored/domain.c | 62 ++++++++++++++++++++++++----------------
 1 file changed, 37 insertions(+), 25 deletions(-)

diff --git a/tools/xenstored/domain.c b/tools/xenstored/domain.c
index 7074abd197..2db452144d 100644
--- a/tools/xenstored/domain.c
+++ b/tools/xenstored/domain.c
@@ -569,24 +569,10 @@ static int domain_tree_remove_sub(const void *ctx, struct 
connection *conn,
                                  struct node *node, void *arg)
 {
        struct domain *domain = arg;
-       int ret = WALK_TREE_OK;
-
-       if (node->perms[0].id != domain->domid)
-               return WALK_TREE_OK;
+       bool node_changed = false;
+       unsigned int i;
 
-       if (keep_orphans) {
-               domain_nbentry_dec(NULL, domain->domid);
-               node->perms[0].id = priv_domid;
-               node->acc.memory = 0;
-               domain_nbentry_inc(NULL, priv_domid);
-               if (write_node_raw(NULL, node->name, node, NODE_MODIFY, true)) {
-                       /* That's unfortunate. We only can try to continue. */
-                       syslog(LOG_ERR,
-                              "error when moving orphaned node %s to dom0\n",
-                              node->name);
-               } else
-                       trace("orphaned node %s moved to dom0\n", node->name);
-       } else {
+       if (node->perms[0].id == domain->domid && !keep_orphans) {
                if (rm_node(NULL, ctx, node->name)) {
                        /* That's unfortunate. We only can try to continue. */
                        syslog(LOG_ERR,
@@ -596,10 +582,39 @@ static int domain_tree_remove_sub(const void *ctx, struct 
connection *conn,
                        trace("orphaned node %s deleted\n", node->name);
 
                /* Skip children in all cases in order to avoid more errors. */
-               ret = WALK_TREE_SKIP_CHILDREN;
+               return WALK_TREE_SKIP_CHILDREN;
        }
 
-       return domain->acc_val[ACC_NODES] ? ret : WALK_TREE_SUCCESS_STOP;
+       if (node->perms[0].id == domain->domid) {
+               domain_nbentry_dec(NULL, domain->domid);
+               node->perms[0].id = priv_domid;
+               node->acc.memory = 0;
+               domain_nbentry_inc(NULL, priv_domid);
+               trace("moving orphaned node %s to dom%d\n", node->name,
+                     priv_domid);
+               node_changed = true;
+       }
+
+       for (i = 1; i < node->hdr.num_perms; i++) {
+               if (node->perms[i].id != domain->domid)
+                       continue;
+               memmove(node->perms + i, node->perms + i + 1,
+                       sizeof(*node->perms) * (node->hdr.num_perms - i - 1));
+               node->hdr.num_perms--;
+               i--;
+               node_changed = true;
+       }
+
+       if (node_changed) {
+               if (write_node_raw(NULL, node->name, node, NODE_MODIFY, true)) {
+                       /* That's unfortunate. We only can try to continue. */
+                       syslog(LOG_ERR,
+                              "error when writing modified node %s\n",
+                              node->name);
+               }
+       }
+
+       return WALK_TREE_OK;
 }
 
 static void domain_tree_remove(struct domain *domain)
@@ -607,12 +622,9 @@ static void domain_tree_remove(struct domain *domain)
        int ret;
        struct walk_funcs walkfuncs = { .enter = domain_tree_remove_sub };
 
-       if (domain->acc_val[ACC_NODES]) {
-               ret = walk_node_tree(domain, NULL, "/", &walkfuncs, domain);
-               if (ret == WALK_TREE_ERROR_STOP)
-                       syslog(LOG_ERR,
-                              "error when looking for orphaned nodes\n");
-       }
+       ret = walk_node_tree(domain, NULL, "/", &walkfuncs, domain);
+       if (ret == WALK_TREE_ERROR_STOP)
+               syslog(LOG_ERR, "error when looking for orphaned nodes\n");
 
        walk_node_tree(domain, NULL, "@releaseDomain", &walkfuncs, domain);
        walk_node_tree(domain, NULL, "@introduceDomain", &walkfuncs, domain);
-- 
2.53.0