From: Jérémie Galarneau Date: Thu, 2 Jun 2016 09:19:50 +0000 (-0400) Subject: Fix: reduce scope of kconsumer consumed_pos and produced_pos X-Git-Tag: v2.8.1~18 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=9ffd0032bf2200db796e0a0c875781da6b8bb7ff;p=lttng-tools.git Fix: reduce scope of kconsumer consumed_pos and produced_pos The consumed_pos and produced_pos accesses are protected by the stream mutex, which is fine as-is. However, consumed_pos is passed to consumer_get_consume_start_pos() and is flagged by Coverity as a possible use of a "stale" consumed_pos. From an analyzer's standpoint, this makes sense since both lttng_kconsumer_get_produced_snapshot() and lttng_kconsumer_get_consumed_snapshot() could leave their output parameter uninitialized and return 0 since they both assume that ioctl() will set errno if ret != 0. IOCTL(3P) specifies that errno is only set if ret < 0. A bug in lttng-modules could cause ioctl() to return a positive value, leaving the errno variable unset. In such a case, both functions would return 0, leaving the positions uninitialized. A follow-up fix enforces this assumption (ret never > 0) as part of the kernctl API. Signed-off-by: Jérémie Galarneau --- diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c index b1cc03e86..68dcc0230 100644 --- a/src/common/kernel-consumer/kernel-consumer.c +++ b/src/common/kernel-consumer/kernel-consumer.c @@ -118,7 +118,6 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path, struct lttng_consumer_local_data *ctx) { int ret; - unsigned long consumed_pos, produced_pos; struct lttng_consumer_channel *channel; struct lttng_consumer_stream *stream; @@ -143,6 +142,7 @@ int lttng_kconsumer_snapshot_channel(uint64_t key, char *path, cds_list_for_each_entry(stream, &channel->streams.head, send_node) { /* Are we at a position _before_ the first available packet ? */ bool before_first_packet = true; + unsigned long consumed_pos, produced_pos; health_code_update();