[PATCH 02/11] scsi: devinfo: rework scsi_strcpy_devinfo()

From: Arnd Bergmann <arnd@kernel.org>
To: linux-kernel@vger.kernel.org,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Chris Down <chris@chrisdown.name>,
	Petr Mladek <pmladek@suse.com>,
	Bart Van Assche <bvanassche@acm.org>,
	linux-scsi@vger.kernel.org
Subject: [PATCH 02/11] scsi: devinfo: rework scsi_strcpy_devinfo()
Date: Thu, 28 Mar 2024 15:04:46 +0100	[thread overview]
Message-ID: <20240328140512.4148825-3-arnd@kernel.org> (raw)
In-Reply-To: <20240328140512.4148825-1-arnd@kernel.org>

From: Arnd Bergmann <arnd@arndb.de>

scsi_strcpy_devinfo() appears to work as intended but its semantics are
so confusing that gcc warns about it when -Wstringop-truncation is enabled:

In function 'scsi_strcpy_devinfo',
    inlined from 'scsi_dev_info_list_add_keyed' at drivers/scsi/scsi_devinfo.c:370:2:
drivers/scsi/scsi_devinfo.c:297:9: error: 'strncpy' specified bound 16 equals destination size [-Werror=stringop-truncation]
  297 |         strncpy(to, from, to_length);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reorganize the function to completely separate the nul-terminated from
the space-padded/non-terminated case. The former is just strscpy_pad(),
while the latter does not have a standard function.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/scsi/scsi_devinfo.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
index ba7237e83863..58726c15ebac 100644
--- a/drivers/scsi/scsi_devinfo.c
+++ b/drivers/scsi/scsi_devinfo.c
@@ -290,18 +290,28 @@ static struct scsi_dev_info_list_table *scsi_devinfo_lookup_by_key(int key)
 static void scsi_strcpy_devinfo(char *name, char *to, size_t to_length,
 				char *from, int compatible)
 {
-	size_t from_length;
+	int ret;
 
-	from_length = strlen(from);
-	/* This zero-pads the destination */
-	strncpy(to, from, to_length);
-	if (from_length < to_length && !compatible) {
-		/*
-		 * space pad the string if it is short.
-		 */
-		memset(&to[from_length], ' ', to_length - from_length);
+	if (compatible) {
+		/* This zero-pads and nul-terminates the destination */
+		ret = strscpy_pad(to, from, to_length);
+	} else {
+		/* no nul-termination but space-padding for short strings */
+		size_t from_length = strlen(from);
+		ret = from_length;
+
+		if (from_length > to_length) {
+			from_length = to_length;
+			ret = -E2BIG;
+		}
+
+		memcpy(to, from, from_length);
+
+		if (from_length < to_length)
+			memset(&to[from_length], ' ', to_length - from_length);
 	}
-	if (from_length > to_length)
+
+	if (ret < 0)
 		 printk(KERN_WARNING "%s: %s string '%s' is too long\n",
 			__func__, name, from);
 }
-- 
2.39.2

