Commit 70303420 authored Jun 21, 2018 by Steven Rostedt (VMware)

tracing: Check for no filter when processing event filters



The syzkaller detected a out-of-bounds issue with the events filter code,
specifically here:

	prog[N].pred = NULL;					/* #13 */
	prog[N].target = 1;		/* TRUE */
	prog[N+1].pred = NULL;
	prog[N+1].target = 0;		/* FALSE */
->	prog[N-1].target = N;
	prog[N-1].when_to_branch = false;

As that's the first reference to a "N-1" index, it appears that the code got
here with N = 0, which means the filter parser found no filter to parse
(which shouldn't ever happen, but apparently it did).

Add a new error to the parsing code that will check to make sure that N is
not zero before going into this part of the code. If N = 0, then -EINVAL is
returned, and a error message is added to the filter.

Cc: stable@vger.kernel.org
Fixes: 80765597 ("tracing: Rewrite filter logic to be simpler and faster")
Reported-by: air icy <icytxw@gmail.com>
bugzilla url: https://bugzilla.kernel.org/show_bug.cgi?id=200019


Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent ce397d21

kernel/trace/trace_events_filter.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -78,7 +78,8 @@ static const char * ops[] = { OPS };
		C(TOO_MANY_PREDS, "Too many terms in predicate expression"), \
		C(INVALID_FILTER, "Meaningless filter expression"), \
		C(IP_FIELD_ONLY, "Only 'ip' field is supported for function trace"), \
		C(INVALID_VALUE, "Invalid value (did you forget quotes)?"),
		C(INVALID_VALUE, "Invalid value (did you forget quotes)?"), \
		C(NO_FILTER, "No filter found"),

		#undef C
		#define C(a, b) FILT_ERR_##a
		@@ -550,6 +551,13 @@ predicate_parse(const char *str, int nr_parens, int nr_preds,
		goto out_free;
		}

		if (!N) {
		/* No program? */
		ret = -EINVAL;
		parse_error(pe, FILT_ERR_NO_FILTER, ptr - str);
		goto out_free;
		}

		prog[N].pred = NULL; /* #13 */
		prog[N].target = 1; /* TRUE */
		prog[N+1].pred = NULL;