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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id s1-20020a170902ea0100b001c3be750900sm22314441plg.163.2023.10.02.10.47.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Oct 2023 10:47:45 -0700 (PDT) Date: Mon, 2 Oct 2023 10:47:42 -0700 From: Kees Cook To: Justin Stitt Cc: Sathya Prakash , Sreekanth Reddy , Suganath Prabu Subramani , MPT-FusionLinux.pdl@broadcom.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] scsi: message: fusion: replace deprecated strncpy with strscpy Message-ID: <202310021043.5BCA90FB92@keescook> References: <20230927-strncpy-drivers-message-fusion-mptsas-c-v1-1-edac65cd7010@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230927-strncpy-drivers-message-fusion-mptsas-c-v1-1-edac65cd7010@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Wed, Sep 27, 2023 at 04:43:08AM +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. > > The only caller of mptsas_exp_repmanufacture_info() is > mptsas_probe_one_phy() which can allocate rphy in either > sas_end_device_alloc() or sas_expander_alloc(). Both of which > zero-allocate: > | rdev = kzalloc(sizeof(*rdev), GFP_KERNEL); > ... this is supplied to mptsas_exp_repmanufacture_info() as edev meaning > that no future NUL-padding of edev members is needed. > > 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. > > Note that while `strscpy(dest, src, sizeof(dest))` is more idiomatic > strscpy usage, we should keep `SAS_EXPANDER...LEN` for length arguments > since changing these to sizeof would mean we are getting buffers one > character larger than expected due to the declaration for these members: > | char vendor_id[SAS_EXPANDER_VENDOR_ID_LEN+1]; > | char product_id[SAS_EXPANDER_PRODUCT_ID_LEN+1]; > | char product_rev[SAS_EXPANDER_PRODUCT_REV_LEN+1]; > | char component_vendor_id[SAS_EXPANDER_COMPONENT_VENDOR_ID_LEN+1]; > ... and simply removing the "+1" in conjunction with using sizeof() may > not work as other code may rely on this adjusted buffer length for > sas_expander_device members. I don't agree with this assessment: without the +1, moving to strscpy() could lead to early truncation. I would change all of them to use sizeof(), so that %NUL termination will happen at the right place when a maxmimally sized string source is used. i.e. for this: dst[FOO + 1] = { }; strncpy(dst, src, FOO); we will copy at most FOO bytes into dst, leaving dst[FOO] as '\0'. If we replace it with: strscpy(dst, src, FOO); Then we'll copy at most FOO-1 bytes into dst, setting dst[FOO - 1] = '\0'; So, these need to be adjusted to use sizeof(dst)... -Kees > > 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 > Cc: Kees Cook > Signed-off-by: Justin Stitt > --- > Note: build-tested only. > > Note: similar to drivers/scsi/mpi3mr/mpi3mr_transport.c +212 which uses > strscpy > --- > drivers/message/fusion/mptsas.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c > index 86f16f3ea478..1dc225701a50 100644 > --- a/drivers/message/fusion/mptsas.c > +++ b/drivers/message/fusion/mptsas.c > @@ -2964,15 +2964,15 @@ mptsas_exp_repmanufacture_info(MPT_ADAPTER *ioc, > goto out_free; > > manufacture_reply = data_out + sizeof(struct rep_manu_request); > - strncpy(edev->vendor_id, manufacture_reply->vendor_id, > + strscpy(edev->vendor_id, manufacture_reply->vendor_id, > SAS_EXPANDER_VENDOR_ID_LEN); > - strncpy(edev->product_id, manufacture_reply->product_id, > + strscpy(edev->product_id, manufacture_reply->product_id, > SAS_EXPANDER_PRODUCT_ID_LEN); > - strncpy(edev->product_rev, manufacture_reply->product_rev, > + strscpy(edev->product_rev, manufacture_reply->product_rev, > SAS_EXPANDER_PRODUCT_REV_LEN); > edev->level = manufacture_reply->sas_format; > if (manufacture_reply->sas_format) { > - strncpy(edev->component_vendor_id, > + strscpy(edev->component_vendor_id, > manufacture_reply->component_vendor_id, > SAS_EXPANDER_COMPONENT_VENDOR_ID_LEN); > tmp = (u8 *)&manufacture_reply->component_id; > > --- > base-commit: 6465e260f48790807eef06b583b38ca9789b6072 > change-id: 20230927-strncpy-drivers-message-fusion-mptsas-c-f22d5a4082e2 > > Best regards, > -- > Justin Stitt > -- Kees Cook