[Qemu-devel] [PATCH] migration: fix crash in when incoming client channel setup fails

["Daniel P. Berrangé" <berrange@redhat.com>]

The way we determine if we can start the incoming migration was
changed to use migration_has_all_channels() in:

  commit 428d89084c709e568f9cd301c2f6416a54c53d6d
  Author: Juan Quintela <quintela@redhat.com>
  Date:   Mon Jul 24 13:06:25 2017 +0200

    migration: Create migration_has_all_channels

This method in turn calls multifd_recv_all_channels_created()
which is hardcoded to always return 'true' when multifd is
not in use.

This means that if channel initialization fails with normal
migration, it'll never notice and attempt to start the
incoming migration regardless.

This can be seen, for example, if a client connects to a server
requiring TLS, but has an invalid x509 certificate:

qemu-system-x86_64: The certificate hasn't got a known issuer
qemu-system-x86_64: migration/migration.c:386: process_incoming_migration_co: Assertion `mis->from_src_file' failed.

 #0  0x00007fffebd24f2b in raise () at /lib64/libc.so.6
 #1  0x00007fffebd0f561 in abort () at /lib64/libc.so.6
 #2  0x00007fffebd0f431 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
 #3  0x00007fffebd1d692 in  () at /lib64/libc.so.6
 #4  0x0000555555ad027e in process_incoming_migration_co (opaque=<optimized out>) at migration/migration.c:386
 #5  0x0000555555c45e8b in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at util/coroutine-ucontext.c:116
 #6  0x00007fffebd3a6a0 in __start_context () at /lib64/libc.so.6
 #7  0x0000000000000000 in  ()

To handle the non-multifd case, we check whether mis->from_src_file
is non-NULL.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 migration/migration.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/migration/migration.c b/migration/migration.c
index e1eaa97df4..38ad818b23 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -518,11 +518,12 @@ void migration_ioc_process_incoming(QIOChannel *ioc)
  */
 bool migration_has_all_channels(void)
 {
+    MigrationIncomingState *mis = migration_incoming_get_current();
     bool all_channels;
 
     all_channels = multifd_recv_all_channels_created();
 
-    return all_channels;
+    return all_channels && mis->from_src_file != NULL;
 }
 
 /*
-- 
2.17.0