From 32280e83b555d692e8c7b96563b0ee2037585712 Mon Sep 17 00:00:00 2001
From: Justin Stitt <justinstitt@google.com>
Date: Wed, 9 Aug 2023 18:19:32 +0000
Subject: [PATCH] um: Refactor deprecated strncpy to memcpy
Use `memcpy` since `console_buf` is not expected to be NUL-terminated
and it more accurately describes what is happening with the buffers
`console_buf` and `string` as per Kees' analysis [1].
Also mark char buffer as `__nonstring` as per Kees' suggestion [2].
This change now makes it more clear what this code does and that
`console_buf` is not expected to be NUL-terminated.
Link: https://lore.kernel.org/all/202308081708.D5ADC80F@keescook/ [1]
Link: https://github.com/KSPP/linux/issues/90 [2]
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Cc: linux-hardening@vger.kernel.org
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
---
arch/um/drivers/mconsole_kern.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 5026e7b9adfe5..ff4bda95b9c7e 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -554,7 +554,7 @@ struct mconsole_output {
static DEFINE_SPINLOCK(client_lock);
static LIST_HEAD(clients);
-static char console_buf[MCONSOLE_MAX_DATA];
+static char console_buf[MCONSOLE_MAX_DATA] __nonstring;
static void console_write(struct console *console, const char *string,
unsigned int len)
@@ -567,7 +567,7 @@ static void console_write(struct console *console, const char *string,
while (len > 0) {
n = min((size_t) len, ARRAY_SIZE(console_buf));
- strncpy(console_buf, string, n);
+ memcpy(console_buf, string, n);
string += n;
len -= n;
--
2.30.2