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tracing: Fix infinite loop in tracing_read_pipe on overflowed print_trace_line 

commit c1ac03af6e 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@huawei.com

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 088b1e427d ("ftrace: pipe fixes")
Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Yang Jihong 2022-11-29 19:30:09 +08:00 committed by Greg Kroah-Hartman
parent 67a4e294c4
commit 61d589b402
1 changed files with 14 additions and 1 deletions
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15
kernel/trace/trace.c
View File

@ -5226,7 +5226,20 @@ 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;
}