NSS: allow removing entries from netgroup hash table

There is a timed desctructor in the nss responder that, when the
entry timeout passes, removes the netgroup from the hash table while
the netgroup is freed. This patch adds a hash delete callback so that if the
netgroup is removed from the hash table with hash_delete, its hash table
pointer will be invalidated. Later, when the entry is being freed, the
destructor won't attempt to remove it from the hash table.

3 files changed, 32 insertions, 1 deletions

diff --git a/src/responder/nss/nsssrv.c b/src/responder/nss/nsssrv.c
index ebad1501..7bc49e3e 100644
--- a/src/responder/nss/nsssrv.c
+++ b/src/responder/nss/nsssrv.c
@@ -35,6 +35,7 @@
 #include "responder/nss/nsssrv.h"
 #include "responder/nss/nsssrv_private.h"
 #include "responder/nss/nsssrv_mmap_cache.h"
+#include "responder/nss/nsssrv_netgroup.h"
 #include "responder/common/negcache.h"
 #include "db/sysdb.h"
 #include "confdb/confdb.h"
@@ -477,7 +478,8 @@ int nss_process_init(TALLOC_CTX *mem_ctx,
     }
 
     /* Create the lookup table for netgroup results */
-    hret = sss_hash_create(nctx, 10, &nctx->netgroups);
+    hret = sss_hash_create_ex(nctx, 10, &nctx->netgroups, 0, 0, 0, 0,
+                              netgroup_hash_delete_cb, NULL);
     if (hret != HASH_SUCCESS) {
         DEBUG(0,("Unable to initialize netgroup hash table\n"));
         ret = EIO;
diff --git a/src/responder/nss/nsssrv_netgroup.c b/src/responder/nss/nsssrv_netgroup.c
index 18cd0da4..e1d3a052 100644
--- a/src/responder/nss/nsssrv_netgroup.c
+++ b/src/responder/nss/nsssrv_netgroup.c
@@ -142,6 +142,12 @@ static int netgr_hash_remove (TALLOC_CTX *ctx)
     struct getent_ctx *netgr =
             talloc_get_type(ctx, struct getent_ctx);
 
+    if (netgr->lookup_table == NULL) {
+        DEBUG(SSSDBG_TRACE_LIBS, ("netgroup [%s] was already removed\n",
+                                  netgr->name));
+        return EOK;
+    }
+
     key.type = HASH_KEY_STRING;
     key.str = netgr->name;
 
@@ -1004,3 +1010,24 @@ int nss_cmd_endnetgrent(struct cli_ctx *client)
     sss_cmd_done(client, NULL);
     return EOK;
 }
+
+void
+netgroup_hash_delete_cb(hash_entry_t *item,
+                        hash_destroy_enum deltype, void *pvt)
+{
+    struct getent_ctx *netgr;
+
+    if (deltype != HASH_ENTRY_DESTROY) {
+        return;
+    }
+
+    netgr = talloc_get_type(item->value.ptr, struct getent_ctx);
+    if (!netgr) {
+        DEBUG(SSSDBG_OP_FAILURE, ("Invalid netgroup\n"));
+        return;
+    }
+
+    /* So that the destructor wouldn't attempt to remove the netgroup from hash
+     * table */
+    netgr->lookup_table = NULL;
+}
diff --git a/src/responder/nss/nsssrv_netgroup.h b/src/responder/nss/nsssrv_netgroup.h
index ed345c43..a909abed 100644
--- a/src/responder/nss/nsssrv_netgroup.h
+++ b/src/responder/nss/nsssrv_netgroup.h
@@ -31,4 +31,6 @@ int nss_cmd_setnetgrent(struct cli_ctx *cctx);
 int nss_cmd_getnetgrent(struct cli_ctx *cctx);
 int nss_cmd_endnetgrent(struct cli_ctx *cctx);
 
+void netgroup_hash_delete_cb(hash_entry_t *item,
+                             hash_destroy_enum deltype, void *pvt);
 #endif /* NSSRV_NETGROUP_H_ */