| Message ID | 20230809-arch-um-v3-1-f63e1122d77e@google.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | be8dffa04de3894bad0bf31d1531a2f06353b70e |
| Headers | show |
| Series | [v3] um: refactor deprecated strncpy to memcpy | expand |
On Wed, Aug 09, 2023 at 06:19:32PM +0000, Justin Stitt wrote: > 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> Thanks for digging through this! Reviewed-by: Kees Cook <keescook@chromium.org>
On Wed, 09 Aug 2023 18:19:32 +0000, Justin Stitt wrote: > 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. > > [...] Applied to for-next/hardening, thanks! [1/1] um: refactor deprecated strncpy to memcpy https://git.kernel.org/kees/c/be8dffa04de3 Take care,
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;
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(-) --- base-commit: c1a515d3c0270628df8ae5f5118ba859b85464a2 change-id: 20230807-arch-um-3ef24413427e Best regards, -- Justin Stitt <justinstitt@google.com>