linux-hardening - [PATCH v3] scsi: target: Replace strlcpy with strscpy

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Date:   Thu, 31 Aug 2023 14:36:38 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3] scsi: target: Replace strlcpy with strscpy

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@...il.com>
---
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@gmail.com/

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

 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