linux-kernel - [PATCH 2/4 v2] init: boot_command

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Date:   Mon, 10 Feb 2020 06:45:03 -0800
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, Mark Salyzyn <salyzyn@...roid.com>,
        "Theodore Ts'o" <tytso@....edu>, Kees Cook <keescook@...omium.org>
Subject: [PATCH 2/4 v2] init: boot_command_line can be truncated

boot_command_line may be truncated, use strnlen, strnstr and strlcpy
to handle it.

Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
Cc: linux-kernel@...r.kernel.org
Cc: kernel-team@...roid.com
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Kees Cook <keescook@...omium.org>
---
 init/main.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/init/main.c b/init/main.c
index a58b72c9433e7..9f4ce0356057e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -536,7 +536,7 @@ static void __init setup_command_line(char *command_line)
 	if (extra_init_args)
 		ilen = strlen(extra_init_args) + strlen(argsep_str);
 
-	len = xlen + strlen(boot_command_line) + 1;
+	len = xlen + strnlen(boot_command_line, sizeof(boot_command_line)) + 1;
 
 	saved_command_line = memblock_alloc(len + ilen, SMP_CACHE_BYTES);
 	if (!saved_command_line)
@@ -555,7 +555,7 @@ static void __init setup_command_line(char *command_line)
 		strcpy(saved_command_line, extra_command_line);
 		strcpy(static_command_line, extra_command_line);
 	}
-	strcpy(saved_command_line + xlen, boot_command_line);
+	strlcpy(saved_command_line + xlen, boot_command_line, len - xlen);
 	strcpy(static_command_line + xlen, command_line);
 
 	if (ilen) {
@@ -565,7 +565,8 @@ static void __init setup_command_line(char *command_line)
 		 * to init.
 		 */
 		len = strlen(saved_command_line);
-		if (!strstr(boot_command_line, argsep_str)) {
+		if (!strnstr(boot_command_line, argsep_str,
+			     sizeof(boot_command_line))) {
 			strcpy(saved_command_line + len, argsep_str);
 			len += strlen(argsep_str);
 		} else
@@ -669,7 +670,7 @@ void __init parse_early_param(void)
 		return;
 
 	/* All fall through to do_early_param. */
-	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+	strlcpy(tmp_cmdline, boot_command_line, sizeof(boot_command_line));
 	parse_early_options(tmp_cmdline);
 	done = 1;
 }
-- 
2.25.0.341.g760bfbb309-goog