Messages in this thread Patch in this message | | | From | Yang Jihong <> | Subject | [PATCH v3] tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line | Date | Thu, 24 Nov 2022 20:58:50 +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 | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a7fe0e115272..55733224fa88 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6787,7 +6787,27 @@ 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 trace_line of the tracer overflows seq_file + * buffer, trace_seq_to_user returns -EBUSY. + * In this case, we need to consume it, otherwise, + * while loop will peek this event next time, + * resulting in an infinite loop. + */ + if (trace_seq_has_overflowed(&iter->seq)) { + /* + * Here we only consider the case that one + * print_trace_line() fills the entire trace_seq + * in one shot, in that case, iter->seq.seq.len is zero, + * we simply output a log of too long line to inform the user. + */ + 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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