linux-kernel - [PATCH] scsi: ch: replace deprecated strncpy with strscpy

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Message-ID: <20231023-strncpy-drivers-scsi-ch-c-v1-1-dc67ba8075a3@google.com>
Date:   Mon, 23 Oct 2023 20:20:14 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     "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: ch: 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.

These labels get copied out to the user so lets make sure they are
NUL-terminated and NUL-padded.

vparams is already memset to 0 so we don't need to do any NUL-padding
(like what strncpy() is doing).

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.

Let's also opt to use the more idiomatic strscpy() usage of:
(dest, src, sizeof(dest)) as this more closely ties the destination
buffer to the length.

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/ch.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/ch.c b/drivers/scsi/ch.c
index cb0a399be1cc..2b864061e073 100644
--- a/drivers/scsi/ch.c
+++ b/drivers/scsi/ch.c
@@ -659,19 +659,23 @@ static long ch_ioctl(struct file *file,
 		memset(&vparams,0,sizeof(vparams));
 		if (ch->counts[CHET_V1]) {
 			vparams.cvp_n1  = ch->counts[CHET_V1];
-			strncpy(vparams.cvp_label1,vendor_labels[0],16);
+			strscpy(vparams.cvp_label1, vendor_labels[0],
+				sizeof(vparams.cvp_label1));
 		}
 		if (ch->counts[CHET_V2]) {
 			vparams.cvp_n2  = ch->counts[CHET_V2];
-			strncpy(vparams.cvp_label2,vendor_labels[1],16);
+			strscpy(vparams.cvp_label2, vendor_labels[1],
+				sizeof(vparams.cvp_label2));
 		}
 		if (ch->counts[CHET_V3]) {
 			vparams.cvp_n3  = ch->counts[CHET_V3];
-			strncpy(vparams.cvp_label3,vendor_labels[2],16);
+			strscpy(vparams.cvp_label3, vendor_labels[2],
+				sizeof(vparams.cvp_label3));
 		}
 		if (ch->counts[CHET_V4]) {
 			vparams.cvp_n4  = ch->counts[CHET_V4];
-			strncpy(vparams.cvp_label4,vendor_labels[3],16);
+			strscpy(vparams.cvp_label4, vendor_labels[3],
+				sizeof(vparams.cvp_label4));
 		}
 		if (copy_to_user(argp, &vparams, sizeof(vparams)))
 			return -EFAULT;

---
base-commit: 9c5d00cb7b6bbc5a7965d9ab7d223b5402d1f02c
change-id: 20231023-strncpy-drivers-scsi-ch-c-23b1cdac43cc

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