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um: Refactor deprecated strncpy to memcpy

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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>
This commit is contained in:
Justin Stitt 2023-08-09 18:19:32 +00:00 committed by Richard Weinberger
parent ab7ca2eb63
commit 32280e83b5
1 changed files with 2 additions and 2 deletions
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4
arch/um/drivers/mconsole_kern.c
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@ -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;