On Thu, Nov 01, 2018 at 06:17:10PM +0800, Fei Li wrote:
> When multifd is used during migration, a segmentaion fault will
> occur in the source when multifd_save_cleanup() is called again if
> the multifd_send_state has been freed in earlier error handling. This
> can happen when migrate_fd_connect() fails and multifd_fd_cleanup()
> is called, and then multifd_new_send_channel_async() fails and
> multifd_save_cleanup() is called again.
>
> If the QIOChannel *c of multifd_recv_state->params[i] (p->c) is not
> initialized, there is no need to close the channel. Or else a
> segmentation fault will occur in multifd_recv_terminate_threads()
> when multifd_recv_initial_packet() fails.
It's a bit odd to me when I see that multifd_send_thread() calls
multifd_send_terminate_threads(). Is that the reason that you
encountered the problem?
Instead of checking all these null pointers, IMHO we should just let
multifd_send_terminate_threads() be called only in the main thread...
>
> Signed-off-by: Fei Li <f...@suse.com>
> ---
> migration/ram.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 7e7deec4d8..4db3b3e8f4 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -907,6 +907,11 @@ static void multifd_send_terminate_threads(Error *err)
> }
> }
>
> + /* in case multifd_send_state has been freed earlier */
> + if (!multifd_send_state) {
> + return;
> + }
> +
> for (i = 0; i < migrate_multifd_channels(); i++) {
> MultiFDSendParams *p = &multifd_send_state->params[i];
>
> @@ -922,7 +927,7 @@ int multifd_save_cleanup(Error **errp)
> int i;
> int ret = 0;
>
> - if (!migrate_use_multifd()) {
> + if (!migrate_use_multifd() || !multifd_send_state) {
> return 0;
> }
> multifd_send_terminate_threads(NULL);
> @@ -960,7 +965,7 @@ static void multifd_send_sync_main(void)
> {
> int i;
>
> - if (!migrate_use_multifd()) {
> + if (!migrate_use_multifd() || !multifd_send_state) {
> return;
> }
> if (multifd_send_state->pages->used) {
> @@ -1070,6 +1075,10 @@ static void multifd_new_send_channel_async(QIOTask
> *task, gpointer opaque)
> QIOChannel *sioc = QIO_CHANNEL(qio_task_get_source(task));
> Error *local_err = NULL;
>
> + if (!multifd_send_state) {
> + return;
> + }
> +
> if (qio_task_propagate_error(task, &local_err)) {
> if (multifd_save_cleanup(&local_err) != 0) {
> migrate_set_error(migrate_get_current(), local_err);
> @@ -1131,7 +1140,7 @@ struct {
> uint64_t packet_num;
> } *multifd_recv_state;
>
> -static void multifd_recv_terminate_threads(Error *err)
> +static void multifd_recv_terminate_threads(Error *err, bool channel)
> {
> int i;
>
> @@ -1145,6 +1154,11 @@ static void multifd_recv_terminate_threads(Error *err)
> }
> }
>
> + /* in case p->c is not initialized */
> + if (!channel) {
> + return;
> + }
> +
> for (i = 0; i < migrate_multifd_channels(); i++) {
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> @@ -1166,7 +1180,7 @@ int multifd_load_cleanup(Error **errp)
> if (!migrate_use_multifd()) {
> return 0;
> }
> - multifd_recv_terminate_threads(NULL);
> + multifd_recv_terminate_threads(NULL, true);
> for (i = 0; i < migrate_multifd_channels(); i++) {
> MultiFDRecvParams *p = &multifd_recv_state->params[i];
>
> @@ -1269,7 +1283,7 @@ static void *multifd_recv_thread(void *opaque)
> }
>
> if (local_err) {
> - multifd_recv_terminate_threads(local_err);
> + multifd_recv_terminate_threads(local_err, true);
> }
> qemu_mutex_lock(&p->mutex);
> p->running = false;
> @@ -1331,7 +1345,7 @@ bool multifd_recv_new_channel(QIOChannel *ioc)
>
> id = multifd_recv_initial_packet(ioc, &local_err);
> if (id < 0) {
> - multifd_recv_terminate_threads(local_err);
> + multifd_recv_terminate_threads(local_err, false);
> return false;
> }
>
> @@ -1339,7 +1353,7 @@ bool multifd_recv_new_channel(QIOChannel *ioc)
> if (p->c != NULL) {
> error_setg(&local_err, "multifd: received id '%d' already setup'",
> id);
> - multifd_recv_terminate_threads(local_err);
> + multifd_recv_terminate_threads(local_err, true);
> return false;
> }
> p->c = ioc;
> --
> 2.13.7
>
Regards,
--
Peter Xu
