linux-hardening - [PATCH 05/10] scsi: aacraid: linit: Replace snprintf() with the safer scnprintf() variant

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Date: Thu,  8 Feb 2024 08:44:17 +0000
From: Lee Jones <lee@...nel.org>
To: lee@...nel.org
Cc: linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	"PMC-Sierra, Inc" <aacraid@...-sierra.com>,
	linux-scsi@...r.kernel.org
Subject: [PATCH 05/10] scsi: aacraid: linit: Replace snprintf() with the safer scnprintf() variant

There is a general misunderstanding amongst engineers that {v}snprintf()
returns the length of the data *actually* encoded into the destination
array.  However, as per the C99 standard {v}snprintf() really returns
the length of the data that *would have been* written if there were
enough space for it.  This misunderstanding has led to buffer-overruns
in the past.  It's generally considered safer to use the {v}scnprintf()
variants in their place (or even sprintf() in simple cases).  So let's
do that.

Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Signed-off-by: Lee Jones <lee@...nel.org>
---
Cc: Adaptec OEM Raid Solutions <aacraid@...rosemi.com>
Cc: "James E.J. Bottomley" <jejb@...ux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
Cc: "PMC-Sierra, Inc" <aacraid@...-sierra.com>
Cc: linux-scsi@...r.kernel.org
---
 drivers/scsi/aacraid/linit.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/aacraid/linit.c b/drivers/scsi/aacraid/linit.c
index 69526e2bd2e78..0e47d9c4cff23 100644
--- a/drivers/scsi/aacraid/linit.c
+++ b/drivers/scsi/aacraid/linit.c
@@ -583,7 +583,7 @@ static ssize_t aac_show_unique_id(struct device *dev,
 	if (sdev_channel(sdev) == CONTAINER_CHANNEL)
 		memcpy(sn, aac->fsa_dev[sdev_id(sdev)].identifier, sizeof(sn));
 
-	return snprintf(buf, 16 * 2 + 2,
+	return scnprintf(buf, 16 * 2 + 2,
 		"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X\n",
 		sn[0], sn[1], sn[2], sn[3],
 		sn[4], sn[5], sn[6], sn[7],
@@ -1302,13 +1302,13 @@ static ssize_t aac_show_serial_number(struct device *device,
 	int len = 0;
 
 	if (le32_to_cpu(dev->adapter_info.serial[0]) != 0xBAD0)
-		len = snprintf(buf, 16, "%06X\n",
+		len = scnprintf(buf, 16, "%06X\n",
 		  le32_to_cpu(dev->adapter_info.serial[0]));
 	if (len &&
 	  !memcmp(&dev->supplement_adapter_info.mfg_pcba_serial_no[
 	    sizeof(dev->supplement_adapter_info.mfg_pcba_serial_no)-len],
 	  buf, len-1))
-		len = snprintf(buf, 16, "%.*s\n",
+		len = scnprintf(buf, 16, "%.*s\n",
 		  (int)sizeof(dev->supplement_adapter_info.mfg_pcba_serial_no),
 		  dev->supplement_adapter_info.mfg_pcba_serial_no);
 
-- 
2.43.0.594.gd9cf4e227d-goog