[PATCH] tracing/fprobe: Roll back on enable_trace_fprobe() failure

[Raushan Patel <raushan.jhon@gmail.com>]

enable_trace_fprobe() sets the file link or the TP_FLAG_PROFILE flag and
then registers each trace_fprobe in the probe list. If
__register_trace_fprobe() fails partway through, the function returns
immediately without unregistering the trace_fprobes it already registered
or undoing the file link / flag it set, leaving the event half-enabled and
leaking the registered fprobe(s).

enable_trace_kprobe() already handles this with a rollback path. Do the
same for fprobe: on failure, unregister all probes and clear the file link
or profile flag.

Fixes: 334e5519c375 ("tracing/probes: Add fprobe events for tracing function entry and exit.")
Cc: stable@vger.kernel.org
Signed-off-by: Raushan Patel <raushan.jhon@gmail.com>
---
 kernel/trace/trace_fprobe.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 9f5f08c0e7c2..3120403a5b60 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -1481,11 +1481,21 @@ static int enable_trace_fprobe(struct trace_event_call *call,
 		list_for_each_entry(tf, trace_probe_probe_list(tp), tp.list) {
 			ret = __register_trace_fprobe(tf);
 			if (ret < 0)
-				return ret;
+				goto err;
 		}
 	}
 
 	return 0;
+
+err:
+	/* Failed to enable one of them. Roll back all */
+	list_for_each_entry(tf, trace_probe_probe_list(tp), tp.list)
+		__unregister_trace_fprobe(tf);
+	if (file)
+		trace_probe_remove_file(tp, file);
+	else
+		trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
+	return ret;
 }
 
 /*
-- 
2.53.0