[PATCH v2 6/9] tracing/filters: Skip second character of '&&' and '||' in calc_stack()

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

In calc_stack(), when encountering '||' or '&&' (where str[i+1] == str[i]),
the loop sets 'is_pred = false' and continues without advancing 'i' past
the second character of the operator. On the next iteration, the second '|'
or '&' sees str[i+1] != str[i], breaks out of the switch statement, and is
counted as the start of a new predicate (incrementing nr_preds and setting
is_pred = true).

Consequently, a trailing logical operator (e.g. 'common_pid == 1 ||') is
counted as having 2 predicates instead of 1, and any subsequent non-space
character before a delimiter fails to increment nr_preds.

Increment 'i' when matching '||' or '&&' so the entire two-character
operator is skipped.

Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
 kernel/trace/trace_events_filter.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 3bd0b47a627f..bcd37fd6c109 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -2208,6 +2208,7 @@ static int calc_stack(const char *str, int *parens, int *preds, int *err)
 		case '&':
 			if (str[i+1] != str[i])
 				break;
+			i++;
 			is_pred = false;
 			continue;
 		case '(':