This is a note to let you know that I've just added the patch titled
tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-fix-infinite-loop-in-tracing_read_pipe-on-overflowed-print_trace_line.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c1ac03af6ed45d05786c219d102f37eb44880f28 Mon Sep 17 00:00:00 2001
From: Yang Jihong <yangjihong1@xxxxxxxxxx>
Date: Tue, 29 Nov 2022 19:30:09 +0800
Subject: tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line
From: Yang Jihong <yangjihong1@xxxxxxxxxx>
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@xxxxxxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 088b1e427dbba ("ftrace: pipe fixes")
Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5798,7 +5798,20 @@ waitagain:
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;
}
Patches currently in stable-queue which might be from yangjihong1@xxxxxxxxxx are
queue-4.14/blktrace-fix-output-non-blktrace-event-when-blk_clas.patch
queue-4.14/tracing-fix-infinite-loop-in-tracing_read_pipe-on-overflowed-print_trace_line.patch
