tracing/boot: Replace strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value of -E2BIG
is used to check for truncation instead of sizeof(dest).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Link: https://lore.kernel.org/linux-trace-kernel/20230613004125.3539934-1-azeemshaikh38@gmail.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 778200dd8edea48ae9f36de6d3d7c7c019d6a557..5fe525f1b8cc2032214468d2e9a8596c113802a3 100644 (file)
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node)
 
        /* Common ftrace options */
        xbc_node_for_each_array_value(node, "options", anode, p) {
-               if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+               if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) {
                        pr_err("String is too long: %s\n", p);
                        continue;
                }
@@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
        const char *p;
 
        xbc_node_for_each_array_value(node, "events", anode, p) {
-               if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+               if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) {
                        pr_err("String is too long: %s\n", p);
                        continue;
                }
@@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 
        p = xbc_node_find_value(enode, "filter", NULL);
        if (p && *p != '\0') {
-               if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+               if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG)
                        pr_err("filter string is too long: %s\n", p);
                else if (apply_event_filter(file, buf) < 0)
                        pr_err("Failed to apply filter: %s\n", buf);
@@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 
        if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) {
                xbc_node_for_each_array_value(enode, "actions", anode, p) {
-                       if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+                       if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG)
                                pr_err("action string is too long: %s\n", p);
                        else if (trigger_process_regex(file, buf) < 0)
                                pr_err("Failed to apply an action: %s\n", p);