From: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx> [ Upstream commit 2ef75e9bd2c998f1c6f6f23a3744136105ddefd5 ] If trace_seq becomes full, trace_seq_vprintf() no longer consumes arguments from va_list, making va_list out of sync with format processing by trace_check_vprintf(). This causes va_arg() in trace_check_vprintf() to return wrong positional argument, which results into a WARN_ON_ONCE() hit. ftrace_stress_test from LTP triggers this situation. Fix it by explicitly avoiding further use if va_list at the point when it's consistency can no longer be guaranteed. Link: https://lkml.kernel.org/r/20211118145516.13219-1-nikita.yushchenko@xxxxxxxxxxxxx Signed-off-by: Nikita Yushchenko <nikita.yushchenko@xxxxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/trace/trace.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5e452dd57af01..18db461f77cdf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3836,6 +3836,18 @@ void trace_check_vprintf(struct trace_iterator *iter, const char *fmt, iter->fmt[i] = '\0'; trace_seq_vprintf(&iter->seq, iter->fmt, ap); + /* + * If iter->seq is full, the above call no longer guarantees + * that ap is in sync with fmt processing, and further calls + * to va_arg() can return wrong positional arguments. + * + * Ensure that ap is no longer used in this case. + */ + if (iter->seq.full) { + p = ""; + break; + } + if (star) len = va_arg(ap, int); -- 2.33.0
