linux-kernel - [for-next][PATCH 12/13] tracing/boot: Replace strlcpy with strscpy

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Date:   Wed, 21 Jun 2023 12:29:35 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        Kees Cook <keescook@...omium.org>
Subject: [for-next][PATCH 12/13] tracing/boot: Replace strlcpy with strscpy

From: Azeem Shaikh <azeemshaikh38@...il.com>

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@...nel.org>
Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_boot.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 778200dd8ede..5fe525f1b8cc 100644
--- 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);
-- 
2.39.2