Messages in this thread |  | | Subject | Re: [PATCH v4] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line | From | Yang Jihong <> | Date | Mon, 12 Dec 2022 10:57:08 +0800 |
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Hello,
PING.
Are there any other problems with this patch?
Thanks, Yang.
On 2022/11/29 19:30, Yang Jihong wrote: > 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; > } >
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