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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id d15-20020a65620f000000b0057e7ae47893sm6448886pgv.47.2023.10.24.11.08.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Oct 2023 11:08:19 -0700 (PDT) Date: Tue, 24 Oct 2023 11:08:19 -0700 From: Kees Cook To: Justin Stitt Cc: Alexandra Winter , Wenjia Zhang , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] s390/qeth: replace deprecated strncpy with strscpy Message-ID: <202310241029.3E4A634@keescook> References: <20231023-strncpy-drivers-s390-net-qeth_core_main-c-v1-1-e7ce65454446@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231023-strncpy-drivers-s390-net-qeth_core_main-c-v1-1-e7ce65454446@google.com> On Mon, Oct 23, 2023 at 07:39:39PM +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 new_entry->dbf_name to be NUL-terminated based on its use with > strcmp(): > | if (strcmp(entry->dbf_name, name) == 0) { > > Moreover, NUL-padding is not required as new_entry is kzalloc'd just > before this assignment: > | new_entry = kzalloc(sizeof(struct qeth_dbf_entry), GFP_KERNEL); > > ... rendering any future NUL-byte assignments (like the ones strncpy() > does) redundant. > > 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. > > 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 struct qeth_dbf_entry { char dbf_name[DBF_NAME_LEN]; The sizeof() replace looks right to me. Reviewed-by: Kees Cook -Kees > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/s390/net/qeth_core_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c > index cd783290bde5..6af2511e070c 100644 > --- a/drivers/s390/net/qeth_core_main.c > +++ b/drivers/s390/net/qeth_core_main.c > @@ -6226,7 +6226,7 @@ static int qeth_add_dbf_entry(struct qeth_card *card, char *name) > new_entry = kzalloc(sizeof(struct qeth_dbf_entry), GFP_KERNEL); > if (!new_entry) > goto err_dbg; > - strncpy(new_entry->dbf_name, name, DBF_NAME_LEN); > + strscpy(new_entry->dbf_name, name, sizeof(new_entry->dbf_name)); > new_entry->dbf_info = card->debug; > mutex_lock(&qeth_dbf_list_mutex); > list_add(&new_entry->dbf_list, &qeth_dbf_list); > > --- > base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c > change-id: 20231023-strncpy-drivers-s390-net-qeth_core_main-c-0b0ee08672ec > > Best regards, > -- > Justin Stitt > > -- Kees Cook