[PATCH v3] scsi: target: Replace strlcpy with strscpy

[Azeem Shaikh]

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 <azeemshaikh38@xxxxxxxxx>
---
v3:
 * Address readability comment.

v2:
 * Replace all instances of strlcpy in this file instead of just 1.
 * https://lore.kernel.org/all/20230830210724.4156575-1-azeemshaikh38@xxxxxxxxx/

v1:
 * https://lore.kernel.org/all/20230830200717.4129442-1-azeemshaikh38@xxxxxxxxx/

 drivers/target/target_core_configfs.c |   24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 936e5ff1b209..d5860c1c1f46 100644
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -1392,16 +1392,16 @@ 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 || len > INQUIRY_VENDOR_LEN) {
 		pr_err("Emulated T10 Vendor Identification exceeds"
 			" INQUIRY_VENDOR_LEN: " __stringify(INQUIRY_VENDOR_LEN)
 			"\n");
@@ -1448,16 +1448,16 @@ 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 || len > INQUIRY_MODEL_LEN) {
 		pr_err("Emulated T10 Vendor exceeds INQUIRY_MODEL_LEN: "
 			 __stringify(INQUIRY_MODEL_LEN)
 			"\n");
@@ -1504,16 +1504,16 @@ 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 || len > INQUIRY_REVISION_LEN) {
 		pr_err("Emulated T10 Revision exceeds INQUIRY_REVISION_LEN: "
 			 __stringify(INQUIRY_REVISION_LEN)
 			"\n");
--
2.42.0.283.g2d96d420d3-goog