[PATCH] trace-cmd: Have tracecmd_write_guest_time_shift() handle NULL tsync

[PATCH] trace-cmd: Have tracecmd_write_guest_time_shift() handle NULL tsync

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

If the clock_context_init() fails, the ctx->instance->tsync will be NULL,
but it may be used in calling tracecmd_write_guest_time_shift(). This will
cause a SEGFAULT as that function expects it to be non NULL.

Test for tsync not NULL and return -1 if it is.

More should be done to warn when this happens, but for now prevent the
SEGFAULT. This makes the code more robust.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 lib/trace-cmd/trace-timesync.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/trace-cmd/trace-timesync.c b/lib/trace-cmd/trace-timesync.c
index bc6430983a96..75c27babfe43 100644
--- a/lib/trace-cmd/trace-timesync.c
+++ b/lib/trace-cmd/trace-timesync.c
@@ -835,7 +835,7 @@ int tracecmd_write_guest_time_shift(struct tracecmd_output *handle,
 	int i, j;
 	int ret = -1;
 
-	if (!tsync->vcpu_count)
+	if (!tsync || !tsync->vcpu_count)
 		return -1;
 	vcount = 3 + (5 * tsync->vcpu_count);
 	vector = calloc(vcount, sizeof(struct iovec));
-- 
2.35.1