From: Justin Stitt <justinstitt@google.com>
To: Richard Weinberger <richard@nod.at>,
Anton Ivanov <anton.ivanov@cambridgegreys.com>,
Johannes Berg <johannes@sipsolutions.net>
Cc: linux-hardening@vger.kernel.org, linux-um@lists.infradead.org,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Justin Stitt <justinstitt@google.com>
Subject: [PATCH v3] um: refactor deprecated strncpy to memcpy
Date: Wed, 09 Aug 2023 18:19:32 +0000 [thread overview]
Message-ID: <20230809-arch-um-v3-1-f63e1122d77e@google.com> (raw)
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>
---
Changes in v3:
- Swap `strtomem` to `memcpy` (thanks Kees)
- Link to v2: https://lore.kernel.org/r/20230808-arch-um-v2-1-5fbe76eaf853@google.com
Changes in v2:
- Keep usage of ARRAY_SIZE (thanks Bill)
- Remove unnecessary import (thanks Kees and Bill)
- Link to v1: https://lore.kernel.org/r/20230807-arch-um-v1-1-86dbbfb59709@google.com
---
Notes:
I only build tested this patch.
---
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 5026e7b9adfe..ff4bda95b9c7 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;
---
base-commit: c1a515d3c0270628df8ae5f5118ba859b85464a2
change-id: 20230807-arch-um-3ef24413427e
Best regards,
--
Justin Stitt <justinstitt@google.com>
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