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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id gx9-20020a056a001e0900b00692b2a63cccsm10621208pfb.210.2023.10.11.16.50.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Oct 2023 16:50:28 -0700 (PDT) Date: Wed, 11 Oct 2023 16:50:24 -0700 From: Kees Cook To: Justin Stitt Cc: Louis Peens , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Paolo Abeni , oss-drivers@corigine.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH] nfp: replace deprecated strncpy with strscpy Message-ID: <202310111649.B1F6BD4159@keescook> References: <20231011-strncpy-drivers-net-ethernet-netronome-nfp-nfpcore-nfp_resource-c-v1-1-7d1c984f0eba@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231011-strncpy-drivers-net-ethernet-netronome-nfp-nfpcore-nfp_resource-c-v1-1-7d1c984f0eba@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 11, 2023 at 09:48:39PM +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 res->name to be NUL-terminated based on its usage with format > strings: > | dev_err(cpp->dev.parent, "Dangling area: %d:%d:%d:0x%0llx-0x%0llx%s%s\n", > | NFP_CPP_ID_TARGET_of(res->cpp_id), > | NFP_CPP_ID_ACTION_of(res->cpp_id), > | NFP_CPP_ID_TOKEN_of(res->cpp_id), > | res->start, res->end, > | res->name ? " " : "", > | res->name ? res->name : ""); > ... and with strcmp() > | if (!strcmp(res->name, NFP_RESOURCE_TBL_NAME)) { > > Moreover, NUL-padding is not required as `res` is already > zero-allocated: > | res = kzalloc(sizeof(*res), GFP_KERNEL); > > 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. > > Let's also opt to use the more idiomatic strscpy() usage of (dest, src, > sizeof(dest)) rather than (dest, src, SOME_LEN). > > Typically the pattern of 1) allocate memory for string, 2) copy string > into freshly-allocated memory is a candidate for kmemdup_nul() but in > this case we are allocating the entirety of the `res` struct and that > should stay as is. As mentioned above, simple 1:1 replacement of strncpy > -> strscpy :) > > 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 > --- > Note: build-tested only. > > Found with: $ rg "strncpy\(" > --- > drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c > index ce7492a6a98f..279ea0b56955 100644 > --- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c > +++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_resource.c > @@ -159,7 +159,7 @@ nfp_resource_acquire(struct nfp_cpp *cpp, const char *name) > if (!res) > return ERR_PTR(-ENOMEM); > > - strncpy(res->name, name, NFP_RESOURCE_ENTRY_NAME_SZ); > + strscpy(res->name, name, sizeof(res->name)); struct nfp_resource { char name[NFP_RESOURCE_ENTRY_NAME_SZ + 1]; Yup, this is doing the implicit string size reduction. Reviewed-by: Kees Cook -- Kees Cook