[PATCH 4.20 62/76] tracing: Fix event filters and triggers to handle negative numbers

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx>

commit 6a072128d262d2b98d31626906a96700d1fc11eb upstream.

Then tracing syscall exit event it is extremely useful to filter exit
codes equal to some negative value, to react only to required errors.
But negative numbers does not work:

[root@snorch sys_exit_read]# echo "ret == -1" > filter
bash: echo: write error: Invalid argument
[root@snorch sys_exit_read]# cat filter
ret == -1
        ^
parse_error: Invalid value (did you forget quotes)?

Similar thing happens when setting triggers.

These is a regression in v4.17 introduced by the commit mentioned below,
testing without these commit shows no problem with negative numbers.

Link: http://lkml.kernel.org/r/20180823102534.7642-1-ptikhomirov@xxxxxxxxxxxxx

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 80765597bc58 ("tracing: Rewrite filter logic to be simpler and faster")
Signed-off-by: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/trace/trace_events_filter.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1301,7 +1301,7 @@ static int parse_pred(const char *str, v
 		/* go past the last quote */
 		i++;
 
-	} else if (isdigit(str[i])) {
+	} else if (isdigit(str[i]) || str[i] == '-') {
 
 		/* Make sure the field is not a string */
 		if (is_string_field(field)) {
@@ -1314,6 +1314,9 @@ static int parse_pred(const char *str, v
 			goto err_free;
 		}
 
+		if (str[i] == '-')
+			i++;
+
 		/* We allow 0xDEADBEEF */
 		while (isalnum(str[i]))
 			i++;