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authorNikita Yushchenko <nikita.yushchenko@virtuozzo.com>2021-11-18 17:55:16 +0300
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2021-11-18 21:10:18 -0500
commit2ef75e9bd2c998f1c6f6f23a3744136105ddefd5 (patch)
tree4d410a3f4373de3ddd33f137f1f3a8d94609e2c3 /kernel
parentc4c1dbcc09e723295969a62aff401815b7ee15f4 (diff)
tracing: Don't use out-of-sync va_list in event printing
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@virtuozzo.com Signed-off-by: Nikita Yushchenko <nikita.yushchenko@virtuozzo.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e3c80cfd4eec..88de94da596b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3812,6 +3812,18 @@ 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);