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Tue, 24 Oct 2023 16:32:45 +0000 (GMT) Message-ID: <6302faa1-b0f3-4405-b4c0-28d309506823@linux.ibm.com> Date: Tue, 24 Oct 2023 18:32:45 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] s390/ctcm: replace deprecated strncpy with strscpy Content-Language: en-GB To: Justin Stitt , Alexandra Winter , Wenjia Zhang , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org References: <20231023-strncpy-drivers-s390-net-ctcm_main-c-v1-1-265db6e78165@google.com> From: Thorsten Winkler In-Reply-To: <20231023-strncpy-drivers-s390-net-ctcm_main-c-v1-1-265db6e78165@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 3anXJQg1cO57P-0sE1YqQFOL8TGs8Bqs X-Proofpoint-ORIG-GUID: RB4OGPEHdMBidTDH8y5UceOR1haKTiMY Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-24_16,2023-10-24_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 bulkscore=0 phishscore=0 mlxscore=0 impostorscore=0 malwarescore=0 suspectscore=0 clxscore=1011 adultscore=0 mlxlogscore=999 priorityscore=1501 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2310170001 definitions=main-2310240142 Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org 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 LGTM, thank you! Reviewed-by: Thorsten Winkler Tested-by: Thorsten Winkler > --- > 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 > >