| Message ID | 20231023-strncpy-drivers-s390-net-ctcm_main-c-v1-1-265db6e78165@google.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Commit | 19d1c64b7741d588af56dc70aa21e028737cd73f |
| Headers | show |
| Series | s390/ctcm: replace deprecated strncpy with strscpy | expand |
On 23.10.23 21:35, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > We expect chid to be NUL-terminated based on its use with format > strings: > > CTCM_DBF_TEXT_(SETUP, CTC_DBF_INFO, "%s(%s) %s", CTCM_FUNTAIL, > chid, ok ? "OK" : "failed"); > > Moreover, NUL-padding is not required as it is _only_ used in this one > instance with a format string. > > Considering the above, a suitable replacement is `strscpy` [2] due to > the fact that it guarantees NUL-termination on the destination buffer > without unnecessarily NUL-padding. > > We can also drop the +1 from chid's declaration as we no longer need to > be cautious about leaving a spot for a NUL-byte. Let's use the more > idiomatic strscpy usage of (dest, src, sizeof(dest)) as this more > closely ties the destination buffer to the length. > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> LGTM, thank you! Reviewed-by: Thorsten Winkler <twinkler@linux.ibm.com> Tested-by: Thorsten Winkler <twinkler@linux.ibm.com> > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/s390/net/ctcm_main.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c > index 6faf27136024..ac15d7c2b200 100644 > --- a/drivers/s390/net/ctcm_main.c > +++ b/drivers/s390/net/ctcm_main.c > @@ -200,13 +200,13 @@ static void channel_free(struct channel *ch) > static void channel_remove(struct channel *ch) > { > struct channel **c = &channels; > - char chid[CTCM_ID_SIZE+1]; > + char chid[CTCM_ID_SIZE]; > int ok = 0; > > if (ch == NULL) > return; > else > - strncpy(chid, ch->id, CTCM_ID_SIZE); > + strscpy(chid, ch->id, sizeof(chid)); > > channel_free(ch); > while (*c) { > > --- > base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c > change-id: 20231023-strncpy-drivers-s390-net-ctcm_main-c-f9180f470c69 > > Best regards, > -- > Justin Stitt <justinstitt@google.com> > >
On Mon, Oct 23, 2023 at 07:35:07PM +0000, Justin Stitt wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > We expect chid to be NUL-terminated based on its use with format > strings: > > CTCM_DBF_TEXT_(SETUP, CTC_DBF_INFO, "%s(%s) %s", CTCM_FUNTAIL, > chid, ok ? "OK" : "failed"); > > Moreover, NUL-padding is not required as it is _only_ used in this one > instance with a format string. > > Considering the above, a suitable replacement is `strscpy` [2] due to > the fact that it guarantees NUL-termination on the destination buffer > without unnecessarily NUL-padding. > > We can also drop the +1 from chid's declaration as we no longer need to > be cautious about leaving a spot for a NUL-byte. Let's use the more > idiomatic strscpy usage of (dest, src, sizeof(dest)) as this more > closely ties the destination buffer to the length. > > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] > Link: https://github.com/KSPP/linux/issues/90 > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Justin Stitt <justinstitt@google.com> Yeah, all looks correct to me. Reviewed-by: Kees Cook <keescook@chromium.org>
Hello: This patch was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: On Mon, 23 Oct 2023 19:35:07 +0000 you wrote: > strncpy() is deprecated for use on NUL-terminated destination strings > [1] and as such we should prefer more robust and less ambiguous string > interfaces. > > We expect chid to be NUL-terminated based on its use with format > strings: > > [...] Here is the summary with links: - s390/ctcm: replace deprecated strncpy with strscpy https://git.kernel.org/netdev/net-next/c/19d1c64b7741 You are awesome, thank you!
diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c index 6faf27136024..ac15d7c2b200 100644 --- a/drivers/s390/net/ctcm_main.c +++ b/drivers/s390/net/ctcm_main.c @@ -200,13 +200,13 @@ static void channel_free(struct channel *ch) static void channel_remove(struct channel *ch) { struct channel **c = &channels; - char chid[CTCM_ID_SIZE+1]; + char chid[CTCM_ID_SIZE]; int ok = 0; if (ch == NULL) return; else - strncpy(chid, ch->id, CTCM_ID_SIZE); + strscpy(chid, ch->id, sizeof(chid)); channel_free(ch); while (*c) {
strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. We expect chid to be NUL-terminated based on its use with format strings: CTCM_DBF_TEXT_(SETUP, CTC_DBF_INFO, "%s(%s) %s", CTCM_FUNTAIL, chid, ok ? "OK" : "failed"); Moreover, NUL-padding is not required as it is _only_ used in this one instance with a format string. Considering the above, a suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. We can also drop the +1 from chid's declaration as we no longer need to be cautious about leaving a spot for a NUL-byte. Let's use the more idiomatic strscpy usage of (dest, src, sizeof(dest)) as this more closely ties the destination buffer to the length. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt <justinstitt@google.com> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/s390/net/ctcm_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c change-id: 20231023-strncpy-drivers-s390-net-ctcm_main-c-f9180f470c69 Best regards, -- Justin Stitt <justinstitt@google.com>