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Message-ID: <6302faa1-b0f3-4405-b4c0-28d309506823@linux.ibm.com> Date: Tue, 24 Oct 2023 18:32:45 +0200 From: Thorsten Winkler <twinkler@...ux.ibm.com> To: Justin Stitt <justinstitt@...gle.com>, Alexandra Winter <wintera@...ux.ibm.com>, Wenjia Zhang <wenjia@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Sven Schnelle <svens@...ux.ibm.com> Cc: linux-s390@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH] s390/ctcm: replace deprecated strncpy with strscpy 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@...r.kernel.org > Signed-off-by: Justin Stitt <justinstitt@...gle.com> LGTM, thank you! Reviewed-by: Thorsten Winkler <twinkler@...ux.ibm.com> Tested-by: Thorsten Winkler <twinkler@...ux.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@...gle.com> > >
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