linux-kernel - [for-next][PATCH 1/2] tracing: Use strncpy instead of memcpy when copying comm for hist triggers

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Date:   Wed, 06 Mar 2019 05:16:58 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [for-next][PATCH 1/2] tracing: Use strncpy instead of memcpy when copying comm for hist
 triggers

From: Tom Zanussi <tom.zanussi@...ux.intel.com>

Because there may be random garbage beyond a string's null terminator,
code that might use the entire comm array e.g. histogram keys, can
give unexpected results if that garbage is copied in too, so avoid
that possibility by using strncpy instead of memcpy.

Link: http://lkml.kernel.org/r/1eb9f096a8086c3c82c7fc087c900005143cec54.1551802084.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_hist.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index c7774fa119a7..ca46339f3009 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -2141,7 +2141,7 @@ static inline void save_comm(char *comm, struct task_struct *task)
 		return;
 	}
 
-	memcpy(comm, task->comm, TASK_COMM_LEN);
+	strncpy(comm, task->comm, TASK_COMM_LEN);
 }
 
 static void hist_elt_data_free(struct hist_elt_data *elt_data)
@@ -3557,7 +3557,7 @@ static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
 	elt_data = context->elt->private_data;
 	track_elt_data = track_data->elt.private_data;
 	if (elt_data->comm)
-		memcpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);
+		strncpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);
 
 	track_data->updated = true;
 
-- 
2.20.1