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b=H4sIADl/DWUC/x2NQQqDMBAAvyJ77oKJxmq/UjxIsmmXQgy7RRTx7 4ZcBuYyc4KSMCm8mhOENlZeUxHzaMB/l/Qh5FAcbGu7drIW9S/J5wOD8EaiyBoS+iUz/io9OjN E84xuGsYeSicLRd7r4z1f1w2gXhc0cwAAAA== X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1695383359; l=2302; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=xmrjKIrKcccHwiQZLHhc+QD8XbzmyrFL8mHFb+Gfs4A=; b=qG0dzg9B6wVI/G86xbbk5dMi4zCmbwp8XMwL+vzCUiOwXjupj59HG/9MKVk0SHfEhICTweQTX Yx6PC25TXp1CgXLQZCRqikxujURFcztXUoBCmjwhvdV8dS45F85qshL X-Mailer: b4 0.12.3 Message-ID: <20230922-strncpy-drivers-isdn-capi-kcapi-c-v1-1-55fcf8b075fb@google.com> Subject: [PATCH] isdn: kcapi: replace deprecated strncpy with strscpy_pad From: Justin Stitt To: Karsten Keil Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Justin Stitt X-Spam-Status: No, score=-8.4 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on pete.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (pete.vger.email [0.0.0.0]); Fri, 22 Sep 2023 04:49:38 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777757663545838284 X-GMAIL-MSGID: 1777757663545838284 `strncpy` is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. `buf` is used in this context as a data buffer with 64 bytes of memory to be occupied by capi_manufakturer. We see the caller capi20_get_manufacturer() passes data.manufacturer as its `buf` argument which is then later passed over to user space. Due to this, let's keep the NUL-padding that strncpy provided by using strscpy_pad so as to not leak any stack data. | cdev->errcode = capi20_get_manufacturer(data.contr, data.manufacturer); | if (cdev->errcode) | return -EIO; | | if (copy_to_user(argp, data.manufacturer, | sizeof(data.manufacturer))) | return -EFAULT; Perhaps this would also be a good instance to use `strtomem_pad` for but in my testing the compiler was not able to determine the size of `buf` -- even with all the hints. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Signed-off-by: Justin Stitt Reviewed-by: Kees Cook --- Note: build-tested only. --- drivers/isdn/capi/kcapi.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- base-commit: 2cf0f715623872823a72e451243bbf555d10d032 change-id: 20230922-strncpy-drivers-isdn-capi-kcapi-c-516f17f59684 Best regards, -- Justin Stitt diff --git a/drivers/isdn/capi/kcapi.c b/drivers/isdn/capi/kcapi.c index ae24848af233..136ba9fe55e0 100644 --- a/drivers/isdn/capi/kcapi.c +++ b/drivers/isdn/capi/kcapi.c @@ -732,7 +732,7 @@ u16 capi20_get_manufacturer(u32 contr, u8 buf[CAPI_MANUFACTURER_LEN]) u16 ret; if (contr == 0) { - strncpy(buf, capi_manufakturer, CAPI_MANUFACTURER_LEN); + strscpy_pad(buf, capi_manufakturer, CAPI_MANUFACTURER_LEN); return CAPI_NOERROR; } @@ -740,7 +740,7 @@ u16 capi20_get_manufacturer(u32 contr, u8 buf[CAPI_MANUFACTURER_LEN]) ctr = get_capi_ctr_by_nr(contr); if (ctr && ctr->state == CAPI_CTR_RUNNING) { - strncpy(buf, ctr->manu, CAPI_MANUFACTURER_LEN); + strscpy_pad(buf, ctr->manu, CAPI_MANUFACTURER_LEN); ret = CAPI_NOERROR; } else ret = CAPI_REGNOTINSTALLED;