Messages in this thread Patch in this message | | | From | Nikita Yushchenko <> | Subject | [PATCH] trace: don't use out-of-sync va_list in event printing | Date | Thu, 18 Nov 2021 08:44:53 +0300 |
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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.
Signed-off-by: Nikita Yushchenko <nikita.yushchenko@virtuozzo.com> --- kernel/trace/trace.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index a1adb29ef5c1..3f527c2e08f2 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3826,6 +3826,18 @@ 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); -- 2.30.2
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