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From:   Romain Perier <romain.perier@gmail.com>
To:     Kees Cook <keescook@chromium.org>,
        kernel-hardening@lists.openwall.com,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Cc:     Romain Perier <romain.perier@gmail.com>,
        linux-scsi@vger.kernel.org, target-devel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 14/20] target: Manual replacement of the deprecated strlcpy() with return values
Date:   Mon, 22 Feb 2021 16:12:25 +0100
Message-Id: <20210222151231.22572-15-romain.perier@gmail.com>
In-Reply-To: <20210222151231.22572-1-romain.perier@gmail.com>
References: <20210222151231.22572-1-romain.perier@gmail.com>
MIME-Version: 1.0
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The strlcpy() reads the entire source buffer first, it is dangerous if
the source buffer lenght is unbounded or possibility non NULL-terminated.
It can lead to linear read overflows, crashes, etc...

As recommended in the deprecated interfaces [1], it should be replaced
by strscpy.

This commit replaces all calls to strlcpy that handle the return values
by the corresponding strscpy calls with new handling of the return
values (as it is quite different between the two functions).

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy

Signed-off-by: Romain Perier <romain.perier@gmail.com>
---
 drivers/target/target_core_configfs.c |   33 +++++++++------------------------
 1 file changed, 9 insertions(+), 24 deletions(-)

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index f04352285155..676215cd8847 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -1325,16 +1325,11 @@ 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)) {
-		/* Strip any newline added from userspace. */
-		stripped = strstrip(buf);
-		len = strlen(stripped);
-	}
-	if (len > INQUIRY_VENDOR_LEN) {
+	len = strscpy(buf, page, sizeof(buf));
+	if (len == -E2BIG) {
 		pr_err("Emulated T10 Vendor Identification exceeds"
 			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
 			"\n");
@@ -1381,16 +1376,11 @@ 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)) {
-		/* Strip any newline added from userspace. */
-		stripped = strstrip(buf);
-		len = strlen(stripped);
-	}
-	if (len > INQUIRY_MODEL_LEN) {
+	len = strscpy(buf, page, sizeof(buf));
+	if (len == -E2BIG) {
 		pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: "
 			 __stringify(INQUIRY_MODEL_LEN)
 			"\n");
@@ -1437,16 +1427,11 @@ 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)) {
-		/* Strip any newline added from userspace. */
-		stripped = strstrip(buf);
-		len = strlen(stripped);
-	}
-	if (len > INQUIRY_REVISION_LEN) {
+	len = strscpy(buf, page, sizeof(buf));
+	if (len == -E2BIG) {
 		pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: "
 			 __stringify(INQUIRY_REVISION_LEN)
 			"\n");