From 517a99c5fba163bf684978fe3d9476b619481391 Mon Sep 17 00:00:00 2001

From: Juan Quintela <quintela@redhat.com>

Date: Tue, 3 Mar 2020 14:51:42 +0000

Subject: [PATCH 10/18] migration/multifd: fix nullptr access in

 multifd_send_terminate_threads

RH-Author: Juan Quintela <quintela@redhat.com>

Message-id: <20200303145143.149290-10-quintela@redhat.com>

Patchwork-id: 94117

O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH v2 09/10] migration/multifd: fix nullptr access in multifd_send_terminate_threads

Bugzilla: 1738451

RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

RH-Acked-by: Peter Xu <peterx@redhat.com>

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

From: Zhimin Feng <fengzhimin1@huawei.com>

If the multifd_send_threads is not created when migration is failed,

multifd_save_cleanup would be called twice. In this senario, the

multifd_send_state is accessed after it has been released, the result

is that the source VM is crashing down.

Here is the coredump stack:

    Program received signal SIGSEGV, Segmentation fault.

    0x00005629333a78ef in multifd_send_terminate_threads (err=err@entry=0x0) at migration/ram.c:1012

    1012            MultiFDSendParams *p = &multifd_send_state->params[i];

    #0  0x00005629333a78ef in multifd_send_terminate_threads (err=err@entry=0x0) at migration/ram.c:1012

    #1  0x00005629333ab8a9 in multifd_save_cleanup () at migration/ram.c:1028

    #2  0x00005629333abaea in multifd_new_send_channel_async (task=0x562935450e70, opaque=<optimized out>) at migration/ram.c:1202

    #3  0x000056293373a562 in qio_task_complete (task=task@entry=0x562935450e70) at io/task.c:196

    #4  0x000056293373a6e0 in qio_task_thread_result (opaque=0x562935450e70) at io/task.c:111

    #5  0x00007f475d4d75a7 in g_idle_dispatch () from /usr/lib64/libglib-2.0.so.0

    #6  0x00007f475d4da9a9 in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0

    #7  0x0000562933785b33 in glib_pollfds_poll () at util/main-loop.c:219

    #8  os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:242

    #9  main_loop_wait (nonblocking=nonblocking@entry=0) at util/main-loop.c:518

    #10 0x00005629334c5acf in main_loop () at vl.c:1810

    #11 0x000056293334d7bb in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4471

If the multifd_send_threads is not created when migration is failed.

In this senario, we don't call multifd_save_cleanup in multifd_new_send_channel_async.

Signed-off-by: Zhimin Feng <fengzhimin1@huawei.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Signed-off-by: Juan Quintela <quintela@redhat.com>

(cherry picked from commit 9c4d333c092e9c26d38f740ff3616deb42f21681)

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 migration/ram.c | 10 +++++++++-

 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/migration/ram.c b/migration/ram.c

index 902c56c..3891eff 100644

--- a/migration/ram.c

+++ b/migration/ram.c

@@ -1229,7 +1229,15 @@ static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)

     trace_multifd_new_send_channel_async(p->id);

     if (qio_task_propagate_error(task, &local_err)) {

         migrate_set_error(migrate_get_current(), local_err);

-        multifd_save_cleanup();

+        /* Error happen, we need to tell who pay attention to me */

+        qemu_sem_post(&multifd_send_state->channels_ready);

+        qemu_sem_post(&p->sem_sync);

+        /*

+         * Although multifd_send_thread is not created, but main migration

+         * thread neet to judge whether it is running, so we need to mark

+         * its status.

+         */

+        p->quit = true;

     } else {

         p->c = QIO_CHANNEL(sioc);

         qio_channel_set_delay(p->c, false);

-- 

1.8.3.1