linux-kernel - [PATCH 4/4] tracing: Make sure variable string fields are NULL-terminated

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Message-Id: <fb97c1e518fb358c12a4057d7445ba2c46956cd7.1522256721.git.tom.zanussi@linux.intel.com>
Date:   Wed, 28 Mar 2018 15:10:56 -0500
From:   Tom Zanussi <tom.zanussi@...ux.intel.com>
To:     rostedt@...dmis.org
Cc:     tglx@...utronix.de, mhiramat@...nel.org, namhyung@...nel.org,
        vedang.patel@...el.com, bigeasy@...utronix.de,
        joel.opensrc@...il.com, joelaf@...gle.com,
        mathieu.desnoyers@...icios.com, baohong.liu@...el.com,
        rajvi.jingar@...el.com, julia@...com, fengguang.wu@...el.com,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [PATCH 4/4] tracing: Make sure variable string fields are NULL-terminated

The strncpy() currently being used for variable string fields can
result in a lack of termination if the string length is equal to the
field size.  Use the safer strscpy() instead, which will guarantee
termination.

Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
 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 ae84470..2751a0f 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -669,7 +669,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
 			char *str_val = (char *)(long)var_ref_vals[var_ref_idx + i];
 			char *str_field = (char *)&entry->fields[n_u64];
 
-			strncpy(str_field, str_val, STR_VAR_LEN_MAX);
+			strscpy(str_field, str_val, STR_VAR_LEN_MAX);
 			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
 		} else {
 			entry->fields[n_u64] = var_ref_vals[var_ref_idx + i];
@@ -3090,7 +3090,7 @@ static inline void __update_field_vars(struct tracing_map_elt *elt,
 			char *str = elt_data->field_var_str[j++];
 			char *val_str = (char *)(uintptr_t)var_val;
 
-			strncpy(str, val_str, STR_VAR_LEN_MAX);
+			strscpy(str, val_str, STR_VAR_LEN_MAX);
 			var_val = (u64)(uintptr_t)str;
 		}
 		tracing_map_set_var(elt, var_idx, var_val);
-- 
1.9.3