[lttng-dev] [PATCH lttng-tools] Fix: consumer-stream: use-after-free of metadata bucket

[Vincent Whitchurch]

When consumer_stream_destroy() is called from, for example, the error
path in setup_metadata(), consumer_stream_free() can end up being called
twice on the same stream.  Since the stream->metadata_bucket is not set
to NULL after being destroyed, it leads to a use-after-free:

 ERROR: AddressSanitizer: heap-use-after-free on address 0x604000000318
 READ of size 8 at 0x604000000318 thread T7
     #0 in metadata_bucket_destroy
     #1 in consumer_stream_free
     #2 in consumer_stream_destroy
     #3 in setup_metadata
     #4 in lttng_ustconsumer_recv_cmd
     #5 in lttng_consumer_recv_cmd
     #6 in consumer_thread_sessiond_poll
     #7 in start_thread nptl/pthread_create.c:481
     #8 in clone (/lib/x86_64-linux-gnu/libc.so.6+0xfcbde)

 0x604000000318 is located 8 bytes inside of 48-byte region [0x604000000310,0x604000000340)
 freed by thread T7 here:
     #0 in __interceptor_free
     #1 in metadata_bucket_destroy
     #2 in consumer_stream_free
     #3 in consumer_stream_destroy
     #4 in clean_channel_stream_list
     #5 in consumer_del_channel
     #6 in consumer_stream_destroy
     #7 in setup_metadata
     #8 in lttng_ustconsumer_recv_cmd
     #9 in lttng_consumer_recv_cmd
     #10 in consumer_thread_sessiond_poll
     #11 in start_thread nptl/pthread_create.c:481

 previously allocated by thread T7 here:
     #0 in __interceptor_calloc
     #1 in zmalloc
     #2 in metadata_bucket_create
     #3 in consumer_stream_enable_metadata_bucketization
     #4 in lttng_ustconsumer_set_stream_ops
     #5 in lttng_ustconsumer_on_recv_stream
     #6 in lttng_consumer_on_recv_stream
     #7 in create_ust_streams
     #8 in ask_channel
     #9 in lttng_ustconsumer_recv_cmd
     #10 in lttng_consumer_recv_cmd
     #11 in consumer_thread_sessiond_poll
     #12 in start_thread nptl/pthread_create.c:481

 Thread T7 created by T0 here:
     #0 in __interceptor_pthread_create
     #1 in main
     #2 in __libc_start_main ../csu/libc-start.c:332

 SUMMARY: AddressSanitizer: heap-use-after-free in metadata_bucket_destroy

Signed-off-by: Vincent Whitchurch <vincent.whitchurch at axis.com>
---
 src/common/consumer/consumer-stream.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/common/consumer/consumer-stream.cpp b/src/common/consumer/consumer-stream.cpp
index 2dc3f002b..481611c3e 100644
--- a/src/common/consumer/consumer-stream.cpp
+++ b/src/common/consumer/consumer-stream.cpp
@@ -988,6 +988,7 @@ void consumer_stream_free(struct lttng_consumer_stream *stream)
 	LTTNG_ASSERT(stream);
 
 	metadata_bucket_destroy(stream->metadata_bucket);
+	stream->metadata_bucket = NULL;
 	call_rcu(&stream->node.head, free_stream_rcu);
 }
 
-- 
2.34.1