From: David Goulet <dgoulet@efficios.com>
Date: Fri, 23 May 2014 14:32:09 +0000 (-0400)
Subject: Fix: deny overwrite mode and num subbuf less than 2
X-Git-Tag: v2.5.0-rc1~21
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=33fbd46910b681a74b2493cff8c86979ec35ccc9;p=lttng-tools.git

Fix: deny overwrite mode and num subbuf less than 2

Also fixed in UST and modules with commit:

(modules) 5140d2b3070f211e6d8a0ad7cb0a190e8b6f3e28
(ust) 3d8e9399b2fb9000b3b55e488a7d04184b5bb56e

Fixes #793

Signed-off-by: David Goulet <dgoulet@efficios.com>
---

diff --git a/doc/man/lttng.1 b/doc/man/lttng.1
index 483df2aef..09c77d1d3 100644
--- a/doc/man/lttng.1
+++ b/doc/man/lttng.1
@@ -402,7 +402,8 @@ Apply to the user-space tracer
 Discard event when subbuffers are full (default)
 .TP
 .BR "\-\-overwrite"
-Flight recorder mode : overwrites events when subbuffers are full
+Flight recorder mode: overwrites events when subbuffers are full. The
+number of subbuffer must be 2 or more.
 .TP
 .BR "\-\-subbuf-size SIZE"
 Subbuffer size in bytes {+k,+M,+G}.
diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index eb516d3b1..2536dc72d 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -933,6 +933,16 @@ int cmd_enable_channel(struct ltt_session *session,
 		attr->attr.switch_timer_interval = 0;
 	}
 
+	/*
+	 * The ringbuffer (both in user space and kernel) behave badly in overwrite
+	 * mode and with less than 2 subbuf so block it right away and send back an
+	 * invalid attribute error.
+	 */
+	if (attr->attr.overwrite && attr->attr.num_subbuf < 2) {
+		ret = LTTNG_ERR_INVALID;
+		goto error;
+	}
+
 	switch (domain->type) {
 	case LTTNG_DOMAIN_KERNEL:
 	{