[lttng-dev] [PATCH lttng-tools 2.10] Fix: do not repurpose iterator while it is being used (register trigger, 2.10)

[Jérémie Galarneau]

Merged in stable-2.10.

Thanks,
Jérémie

On Wed, 12 Dec 2018 at 17:37, Mathieu Desnoyers
<mathieu.desnoyers at efficios.com> wrote:
>
> The hash table iteration uses an iterator that needs to stay valid for
> the next loop. Using that same iterator variable in a nested lookup in a
> different hash table leads to segmentation fault.
>
> This is a 2.10-specific instance of the issue affecting
> bind_trigger_to_matching_channels() which was found in the
> master and 2.11 branches. This one affects
> handle_notification_thread_command_register_trigger().
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> ---
>  src/bin/lttng-sessiond/notification-thread-events.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/bin/lttng-sessiond/notification-thread-events.c b/src/bin/lttng-sessiond/notification-thread-events.c
> index 6777fd6d..f54141e7 100644
> --- a/src/bin/lttng-sessiond/notification-thread-events.c
> +++ b/src/bin/lttng-sessiond/notification-thread-events.c
> @@ -1119,6 +1119,7 @@ int handle_notification_thread_command_register_trigger(
>                         channels_ht_node) {
>                 struct lttng_trigger_list_element *trigger_list_element;
>                 struct lttng_channel_trigger_list *trigger_list;
> +               struct cds_lfht_iter lookup_iter;
>
>                 if (!trigger_applies_to_channel(trigger, channel)) {
>                         continue;
> @@ -1128,8 +1129,8 @@ int handle_notification_thread_command_register_trigger(
>                                 hash_channel_key(&channel->key),
>                                 match_channel_trigger_list,
>                                 &channel->key,
> -                               &iter);
> -               node = cds_lfht_iter_get_node(&iter);
> +                               &lookup_iter);
> +               node = cds_lfht_iter_get_node(&lookup_iter);
>                 assert(node);
>                 trigger_list = caa_container_of(node,
>                                 struct lttng_channel_trigger_list,
> --
> 2.11.0
>


-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com