From: Yang Jihong yangjihong1@huawei.com
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: 088b1e427dbba ("ftrace: pipe fixes") Signed-off-by: Yang Jihong yangjihong1@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- 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 664619b3f1e1..548890c7c0f5 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6802,7 +6802,20 @@ 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; }