[lttng-dev] [PATCH lttng-tools 1/2] Fix: Parenthesize previous statement when adding conditions to a filter

[Jérémie Galarneau]

Not parenthesizing the clauses in a filter string causes JUL events to be
traced even though they are not enabled when an enable-event command is
issued with a filter and the --loglevel-only option.

For instance,

lttng enable-event -j "my_event" --loglevel-only JUL_CONFIG -f "int_loglevel > 0 || int_loglevel < 0"

results in the following filter being applied:

int_loglevel > 0 || int_loglevel < 0 && logger_name == "my_event" && int_loglevel == 700

The resulting expression will always evaluate to true, regardless of the logger
name.

This fix parenthesizes each clause to ensure they are all independently
evaluated and not unintuitively affected by operator precedence.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau at efficios.com>
---
 src/lib/lttng-ctl/lttng-ctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index 9686b7d..f83d053 100644
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -705,7 +705,7 @@ static char *set_jul_filter(const char *filter, struct lttng_event *ev)
 	/* Don't add filter for the '*' event. */
 	if (ev->name[0] != '*') {
 		if (filter) {
-			err = asprintf(&jul_filter, "%s && logger_name == \"%s\"", filter,
+			err = asprintf(&jul_filter, "(%s) && (logger_name == \"%s\")", filter,
 					ev->name);
 		} else {
 			err = asprintf(&jul_filter, "logger_name == \"%s\"", ev->name);
@@ -729,7 +729,7 @@ static char *set_jul_filter(const char *filter, struct lttng_event *ev)
 		if (filter || jul_filter) {
 			char *new_filter;
 
-			err = asprintf(&new_filter, "%s && int_loglevel %s %d",
+			err = asprintf(&new_filter, "(%s) && (int_loglevel %s %d)",
 					jul_filter ? jul_filter : filter, op,
 					ev->loglevel);
 			if (jul_filter) {
-- 
2.1.0