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[34.123.74.161]) by smtp.gmail.com with ESMTPSA id v9-20020a92c809000000b0034ce78e2450sm45948iln.39.2023.08.30.14.53.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Aug 2023 14:53:33 -0700 (PDT) Date: Wed, 30 Aug 2023 21:53:30 +0000 From: Justin Stitt To: Azeem Shaikh Cc: "Martin K. Petersen" , linux-hardening@vger.kernel.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] scsi: target: Replace strlcpy with strscpy Message-ID: <20230830215330.6gyhpq3ohkbbtsam@google.com> References: <20230830210724.4156575-1-azeemshaikh38@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230830210724.4156575-1-azeemshaikh38@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Wed, Aug 30, 2023 at 09:07:24PM +0000, Azeem Shaikh wrote: > strlcpy() reads the entire source buffer first. > This read may exceed the destination size limit. > This is both inefficient and can lead to linear read > overflows if a source string is not NUL-terminated [1]. > In an effort to remove strlcpy() completely [2], replace > strlcpy() here with strscpy(). > > Direct replacement is safe here since return value of -errno > is used to check for truncation instead of sizeof(dest). > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy > [2] https://github.com/KSPP/linux/issues/89 > > Signed-off-by: Azeem Shaikh > --- > v2: > * Replace all instances of strlcpy in this file instead of just 1. > > v1: > * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@gmail.com/ > > drivers/target/target_core_configfs.c | 27 ++++++++++++--------------- > 1 file changed, 12 insertions(+), 15 deletions(-) > > diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c > index 936e5ff1b209..10a22a428267 100644 > --- a/drivers/target/target_core_configfs.c > +++ b/drivers/target/target_core_configfs.c > @@ -1392,16 +1392,15 @@ static ssize_t target_wwn_vendor_id_store(struct config_item *item, > /* +2 to allow for a trailing (stripped) '\n' and null-terminator */ > unsigned char buf[INQUIRY_VENDOR_LEN + 2]; > char *stripped = NULL; > - size_t len; > + ssize_t len; > ssize_t ret; > > - len = strlcpy(buf, page, sizeof(buf)); > - if (len < sizeof(buf)) { > + len = strscpy(buf, page, sizeof(buf)); > + if (len > 0) { > /* Strip any newline added from userspace. */ > stripped = strstrip(buf); > - len = strlen(stripped); > } > - if (len > INQUIRY_VENDOR_LEN) { > + if (len < 0 || strlen(stripped) > INQUIRY_VENDOR_LEN) { > pr_err("Emulated T10 Vendor Identification exceeds" > " INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN) > "\n"); Should we be explicitly checking for `len == -E2BIG` instead of the more generic `len < 0`? Perhaps this is a nitpick but I prefer the former. ... > @@ -1448,16 +1447,15 @@ static ssize_t target_wwn_product_id_store(struct config_item *item, > /* +2 to allow for a trailing (stripped) '\n' and null-terminator */ > unsigned char buf[INQUIRY_MODEL_LEN + 2]; > char *stripped = NULL; > - size_t len; > + ssize_t len; > ssize_t ret; > > - len = strlcpy(buf, page, sizeof(buf)); > - if (len < sizeof(buf)) { > + len = strscpy(buf, page, sizeof(buf)); > + if (len > 0) { > /* Strip any newline added from userspace. */ > stripped = strstrip(buf); > - len = strlen(stripped); > } > - if (len > INQUIRY_MODEL_LEN) { > + if (len < 0 || strlen(stripped) > INQUIRY_MODEL_LEN) { > pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: " > __stringify(INQUIRY_MODEL_LEN) > "\n"); ... and here > @@ -1504,16 +1502,15 @@ static ssize_t target_wwn_revision_store(struct config_item *item, > /* +2 to allow for a trailing (stripped) '\n' and null-terminator */ > unsigned char buf[INQUIRY_REVISION_LEN + 2]; > char *stripped = NULL; > - size_t len; > + ssize_t len; > ssize_t ret; > > - len = strlcpy(buf, page, sizeof(buf)); > - if (len < sizeof(buf)) { > + len = strscpy(buf, page, sizeof(buf)); > + if (len > 0) { > /* Strip any newline added from userspace. */ > stripped = strstrip(buf); > - len = strlen(stripped); > } > - if (len > INQUIRY_REVISION_LEN) { > + if (len < 0 || strlen(stripped) > INQUIRY_REVISION_LEN) { > pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: " > __stringify(INQUIRY_REVISION_LEN) > "\n"); ... and here > -- > 2.42.0.283.g2d96d420d3-goog > > At any rate, this is a worthwhile change for the reasons you mentioned. Reviewed-by: Justin Stitt