migration: Fix error leak in postcopy_ram_listen_thread()

As reported and analyzed by Peter:

https://lore.kernel.org/r/CAFEAcA9otBWtR7rPQ0Y9aBm+7ZWJzd4VWpXrAmGr8XspPn+zpw@mail.gmail.com

Fix it by freeing the error.  When at it, always reset the local_err
pointer in both paths.

Cc: Arun Menon <armenon@redhat.com>
Resolves: Coverity CID 1641390
Fixes: 94272d9b45 ("migration: Capture error in postcopy_ram_listen_thread()")
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20251021220407.2662288-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

diff --git a/migration/savevm.c b/migration/savevm.c
index aafa40d77907ca436e79ff3a4a54c338ab85095f..232cae090b1a45805eaa54bbb0544a370fdb574b 100644 (file)
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2136,17 +2136,18 @@ static void *postcopy_ram_listen_thread(void *opaque)
         if (postcopy_state_get() == POSTCOPY_INCOMING_RUNNING &&
             !migrate_postcopy_ram() && migrate_dirty_bitmaps())
         {
-            error_report("%s: loadvm failed during postcopy: %d. All states "
+            error_report("%s: loadvm failed during postcopy: %d: %s. All states "
                          "are migrated except dirty bitmaps. Some dirty "
                          "bitmaps may be lost, and present migrated dirty "
                          "bitmaps are correctly migrated and valid.",
-                         __func__, load_res);
+                         __func__, load_res, error_get_pretty(local_err));
+            g_clear_pointer(&local_err, error_free);
             load_res = 0; /* prevent further exit() */
         } else {
             error_prepend(&local_err,
                           "loadvm failed during postcopy: %d: ", load_res);
             migrate_set_error(migr, local_err);
-            error_report_err(local_err);
+            g_clear_pointer(&local_err, error_report_err);
             migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_ACTIVE,
                                            MIGRATION_STATUS_FAILED);
         }