From a36580d58f21f305c1f2465acba726c1e9b82ae8 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 25 Sep 2014 20:35:59 -0400 Subject: [PATCH] Fix: lttng-modules teardown NULL pointer OOPS Accessing the lttng channel and lttng session from the metadata ring buffer client is a bad idea, because we don't have any reference ensuring those are valid for the lifetime of the metadata cache. Therefore, rather than keeping a lttng channel as private data pointer for the metadata ring buffer channel, keep a pointer to the metadata cache instead: this will ensure we don't shoot ourself in the foot and access data we for which coherency is not guaranteed (we don't hold any reference to it). Anyway, the only reason why we needed to access the lttng session from the metadata client in the first place was the UUID of the session. Copy it into the metadata cache instead. Signed-off-by: Mathieu Desnoyers --- lttng-events.c | 2 ++ lttng-events.h | 1 + lttng-ring-buffer-metadata-client.h | 10 ++++++---- 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/lttng-events.c b/lttng-events.c index 1fecff8e..b2d0d754 100644 --- a/lttng-events.c +++ b/lttng-events.c @@ -98,6 +98,8 @@ struct lttng_session *lttng_session_create(void) kref_init(&metadata_cache->refcount); session->metadata_cache = metadata_cache; INIT_LIST_HEAD(&metadata_cache->metadata_stream); + memcpy(&metadata_cache->uuid, &session->uuid, + sizeof(metadata_cache->uuid)); list_add(&session->list, &sessions); mutex_unlock(&sessions_mutex); return session; diff --git a/lttng-events.h b/lttng-events.h index b09bd4fc..64a1ac56 100644 --- a/lttng-events.h +++ b/lttng-events.h @@ -333,6 +333,7 @@ struct lttng_metadata_cache { unsigned int metadata_written; /* Number of bytes written in metadata cache */ struct kref refcount; /* Metadata cache usage */ struct list_head metadata_stream; /* Metadata stream list */ + uuid_le uuid; /* Trace session unique ID (copy) */ }; struct lttng_session *lttng_session_create(void); diff --git a/lttng-ring-buffer-metadata-client.h b/lttng-ring-buffer-metadata-client.h index f077f4f6..9e035304 100644 --- a/lttng-ring-buffer-metadata-client.h +++ b/lttng-ring-buffer-metadata-client.h @@ -99,11 +99,12 @@ static void client_buffer_begin(struct lib_ring_buffer *buf, u64 tsc, (struct metadata_packet_header *) lib_ring_buffer_offset_address(&buf->backend, subbuf_idx * chan->backend.subbuf_size); - struct lttng_channel *lttng_chan = channel_get_private(chan); - struct lttng_session *session = lttng_chan->session; + struct lttng_metadata_cache *metadata_cache = + channel_get_private(chan); header->magic = TSDL_MAGIC_NUMBER; - memcpy(header->uuid, session->uuid.b, sizeof(session->uuid)); + memcpy(header->uuid, metadata_cache->uuid.b, + sizeof(metadata_cache->uuid)); header->checksum = 0; /* 0 if unused */ header->content_size = 0xFFFFFFFF; /* in bits, for debugging */ header->packet_size = 0xFFFFFFFF; /* in bits, for debugging */ @@ -239,7 +240,8 @@ struct channel *_channel_create(const char *name, { struct channel *chan; - chan = channel_create(&client_config, name, lttng_chan, buf_addr, + chan = channel_create(&client_config, name, + lttng_chan->session->metadata_cache, buf_addr, subbuf_size, num_subbuf, switch_timer_interval, read_timer_interval); if (chan) { -- 2.34.1