linux-kernel - [PATCH 1/1] x86/kaslr: Replace strlen with strnlen

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Message-Id: <20200803011534.730645-2-nivedita@alum.mit.edu>
Date:   Sun,  2 Aug 2020 21:15:34 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] x86/kaslr: Replace strlen with strnlen

strnlen is safer in case the command line is not NUL-terminated.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 arch/x86/boot/compressed/kaslr.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 903ccdca0551..a5842eea84cb 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -43,6 +43,10 @@
 #define STATIC
 #include <linux/decompress/mm.h>
 
+#define _SETUP
+#include <asm/setup.h>	/* For COMMAND_LINE_SIZE */
+#undef _SETUP
+
 #ifdef CONFIG_X86_5LEVEL
 unsigned int __pgtable_l5_enabled;
 unsigned int pgdir_shift __ro_after_init = 39;
@@ -278,7 +282,7 @@ static void handle_mem_options(void)
 	if (!args)
 		return;
 
-	len = strlen(args);
+	len = strnlen(args, COMMAND_LINE_SIZE-1);
 	tmp_cmdline = malloc(len + 1);
 	if (!tmp_cmdline)
 		error("Failed to allocate space for tmp_cmdline");
@@ -425,7 +429,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
 	cmd_line = get_cmd_line_ptr();
 	/* Calculate size of cmd_line. */
 	if (cmd_line) {
-		cmd_line_size = strlen((char *)cmd_line) + 1;
+		cmd_line_size = strnlen((char *)cmd_line, COMMAND_LINE_SIZE-1) + 1;
 		mem_avoid[MEM_AVOID_CMDLINE].start = cmd_line;
 		mem_avoid[MEM_AVOID_CMDLINE].size = cmd_line_size;
 		add_identity_map(mem_avoid[MEM_AVOID_CMDLINE].start,
-- 
2.26.2