linux-kernel - [PATCH] tracing: avoid string overflow

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Date:   Wed, 28 Mar 2018 16:09:10 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Rajvi Jingar <rajvi.jingar@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] tracing: avoid string overflow

'err' is used as a NUL-terminated string, but using strncpy() with the length
equal to the buffer size may result in lack of the termination:

kernel/trace/trace_events_hist.c: In function 'hist_err_event':
kernel/trace/trace_events_hist.c:396:3: error: 'strncpy' specified bound 256 equals destination size [-Werror=stringop-truncation]
   strncpy(err, var, MAX_FILTER_STR_VAL);

This changes it to use the safer strscpy() instead.

Fixes: f404da6e1d46 ("tracing: Add 'last error' error facility for hist triggers")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 kernel/trace/trace_events_hist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 4f027642ceef..8357f36d7a1e 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -393,7 +393,7 @@ static void hist_err_event(char *str, char *system, char *event, char *var)
 	else if (system)
 		snprintf(err, MAX_FILTER_STR_VAL, "%s.%s", system, event);
 	else
-		strncpy(err, var, MAX_FILTER_STR_VAL);
+		strscpy(err, var, MAX_FILTER_STR_VAL);
 
 	hist_err(str, err);
 }
-- 
2.9.0