tracing: Replace multiple deprecated strncpy with memcpy

strncpy() is deprecated for use on NUL-terminated destination strings [1] and
as such we should prefer more robust and less ambiguous string interfaces.

String copy operations involving manual pointer offset and length
calculations followed by explicit NUL-byte assignments are best changed
to either strscpy or memcpy.

strscpy is not a drop-in replacement as @len would need a one subtracted
from it to avoid truncating the source string.

To not sabotage readability of the current code, use memcpy (retaining
the manual NUL assignment) as this unambiguously describes the desired
behavior.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://github.com/KSPP/linux/issues/90
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: linux-hardening@vger.kernel.org
Link: https://lore.kernel.org/20241014-strncpy-kernel-trace-trace_events_filter-c-v2-1-d821e81e371e@google.com
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 0c611b281a5b5f71ca11de8ccdc939e725725625..78051de581e78536bba3d11eb06004fd9ba44ab9 100644 (file)
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1616,7 +1616,7 @@ static int parse_pred(const char *str, void *data,
                                goto err_free;
                        }
 
-                       strncpy(num_buf, str + s, len);
+                       memcpy(num_buf, str + s, len);
                        num_buf[len] = 0;
 
                        ret = kstrtoul(num_buf, 0, &ip);
@@ -1694,7 +1694,7 @@ static int parse_pred(const char *str, void *data,
                if (!pred->regex)
                        goto err_mem;
                pred->regex->len = len;
-               strncpy(pred->regex->pattern, str + s, len);
+               memcpy(pred->regex->pattern, str + s, len);
                pred->regex->pattern[len] = 0;
 
        } else if (!strncmp(str + i, "CPUS", 4)) {
@@ -1859,7 +1859,7 @@ static int parse_pred(const char *str, void *data,
                if (!pred->regex)
                        goto err_mem;
                pred->regex->len = len;
-               strncpy(pred->regex->pattern, str + s, len);
+               memcpy(pred->regex->pattern, str + s, len);
                pred->regex->pattern[len] = 0;
 
                filter_build_regex(pred);
@@ -1919,7 +1919,7 @@ static int parse_pred(const char *str, void *data,
                        goto err_free;
                }
 
-               strncpy(num_buf, str + s, len);
+               memcpy(num_buf, str + s, len);
                num_buf[len] = 0;
 
                /* Make sure it is a value */