From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47583) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d1H8P-0002cg-Kv for qemu-devel@nongnu.org; Thu, 20 Apr 2017 14:48:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d1H8O-0004pP-6J for qemu-devel@nongnu.org; Thu, 20 Apr 2017 14:48:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37002) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d1H8N-0004p4-Vx for qemu-devel@nongnu.org; Thu, 20 Apr 2017 14:48:52 -0400 Date: Thu, 20 Apr 2017 19:48:43 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20170420184843.GJ2094@work-vm> References: <20170412135312.1686-1-lvivier@redhat.com> <20170412135312.1686-2-lvivier@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170412135312.1686-2-lvivier@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 1/2] migration: don't close a file descriptor while it can be in use List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laurent Vivier Cc: "Michael S . Tsirkin" , Stefan Hajnoczi , Amit Shah , qemu-devel@nongnu.org * Laurent Vivier (lvivier@redhat.com) wrote: > If we close the QEMUFile descriptor in process_incoming_migration_co() > while it has been stopped by an error, the postcopy_ram_listen_thread() > can try to continue to use it. And as the memory has been freed > it is working with an invalid pointer and crashes. > > Fix this by releasing the memory after having managed the error > case (which, in fact, calls exit()) > > Signed-off-by: Laurent Vivier Reviewed-by: Dr. David Alan Gilbert Yes, this took me some thinking about why it got there. (I only managed to reproduce this case once, even with 'tc') 'LISTEN' message via loadvm_postcopy_handle_listen, postcopy state is set to LISTENING sets mis->have_listen_thread starts 'listen' thread Errors while 'loading state of instance...' so fails qemu_loadvm_state_main in loadvm_handle_cmd_packaged fails loadvm_process_command fails qemu_loadvm_state_main fails in qemu_loadvm_state has mis->have_listen_thread process_incoming_migration_co since ret < 0 fails now rather than leaving it to the 'listening thread' - which is probably still alive Dave > --- > migration/migration.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/migration/migration.c b/migration/migration.c > index ad4036f..e024e0a 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -436,9 +436,6 @@ static void process_incoming_migration_co(void *opaque) > qemu_thread_join(&mis->colo_incoming_thread); > } > > - qemu_fclose(f); > - free_xbzrle_decoded_buf(); > - > if (ret < 0) { > migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE, > MIGRATION_STATUS_FAILED); > @@ -447,6 +444,9 @@ static void process_incoming_migration_co(void *opaque) > exit(EXIT_FAILURE); > } > > + qemu_fclose(f); > + free_xbzrle_decoded_buf(); > + > mis->bh = qemu_bh_new(process_incoming_migration_bh, mis); > qemu_bh_schedule(mis->bh); > } > -- > 2.9.3 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK