Commit c42cb66a authored Nov 29, 2022 by Yang Jihong Committed by Greg Kroah-Hartman Jan 18, 2023

tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line

commit c1ac03af6ed45d05786c219d102f37eb44880f28 upstream.

print_trace_line may overflow seq_file buffer. If the event is not
consumed, the while loop keeps peeking this event, causing a infinite loop.

Link: https://lkml.kernel.org/r/20221129113009.182425-1-yangjihong1@huawei.com



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 088b1e42 ("ftrace: pipe fixes")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent cb03fc21

kernel/trace/trace.c

+14 −1

Original line number	Diff line number	Diff line
		@@ -6101,7 +6101,20 @@ tracing_read_pipe(struct file filp, char __user ubuf,

		ret = print_trace_line(iter);
		if (ret == TRACE_TYPE_PARTIAL_LINE) {
		/* don't print partial lines */
		/*
		* If one print_trace_line() fills entire trace_seq in one shot,
		* trace_seq_to_user() will returns -EBUSY because save_len == 0,
		* In this case, we need to consume it, otherwise, loop will peek
		* this event next time, resulting in an infinite loop.
		*/
		if (save_len == 0) {
		iter->seq.full = 0;
		trace_seq_puts(&iter->seq, "[LINE TOO BIG]\n");
		trace_consume(iter);
		break;
		}

		/* In other cases, don't print partial lines */
		iter->seq.seq.len = save_len;
		break;
		}