Messages in this thread Patch in this message | | | From | Yang Jihong <> | Subject | [PATCH v4] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line | Date | Tue, 29 Nov 2022 19:30:09 +0800 |
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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.
Signed-off-by: Yang Jihong <yangjihong1@huawei.com> --- kernel/trace/trace.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a7fe0e115272..de7c99f4b539 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6787,7 +6787,20 @@ 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; } -- 2.30.GIT
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