linux-hardening - [PATCH] scsi: fcoe: replace deprecated strncpy with strscpy

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Message-ID: <20231024-strncpy-drivers-scsi-fcoe-fcoe_sysfs-c-v1-1-1e0026ee032d@google.com>
Date: Tue, 24 Oct 2023 19:52:27 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Hannes Reinecke <hare@...e.de>, "James E.J. Bottomley" <jejb@...ux.ibm.com>, 
	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] scsi: fcoe: replace deprecated strncpy with strscpy

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 `mode` to be NUL-terminated based on its usage with
strcasecmp():

|       ctlr->mode = fcoe_parse_mode(mode);
...
|       static enum fip_conn_type fcoe_parse_mode(const char *buf)
|       {
|       	int i;
|
|       	for (i = 0; i < ARRAY_SIZE(fip_conn_type_names); i++) {
|       		if (strcasecmp(buf, fip_conn_type_names[i]) == 0)
|       			return i;
|       	}
|
|       	return FIP_CONN_TYPE_UNKNOWN;
|       }

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.

We can drop the manual NUL-byte assignment but should keep the newline
removal so newlines don't creep into the string.

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@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/scsi/fcoe/fcoe_sysfs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/scsi/fcoe/fcoe_sysfs.c b/drivers/scsi/fcoe/fcoe_sysfs.c
index e17957f8085c..7a3ca6cd3030 100644
--- a/drivers/scsi/fcoe/fcoe_sysfs.c
+++ b/drivers/scsi/fcoe/fcoe_sysfs.c
@@ -279,12 +279,10 @@ static ssize_t store_ctlr_mode(struct device *dev,
 	if (count > FCOE_MAX_MODENAME_LEN)
 		return -EINVAL;
 
-	strncpy(mode, buf, count);
+	strscpy(mode, buf, count);
 
 	if (mode[count - 1] == '\n')
 		mode[count - 1] = '\0';
-	else
-		mode[count] = '\0';
 
 	switch (ctlr->enabled) {
 	case FCOE_CTLR_ENABLED:

---
base-commit: d88520ad73b79e71e3ddf08de335b8520ae41c5c
change-id: 20231024-strncpy-drivers-scsi-fcoe-fcoe_sysfs-c-0e1dffe82855

Best regards,
--
Justin Stitt <justinstitt@...gle.com>