linux-kernel - [PATCH 5/5] scsi: aacraid: aachba: Replace snprintf() with the safer scnprintf() variant

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Date: Thu, 11 Jan 2024 13:17:26 +0000
From: Lee Jones <lee@...nel.org>
To: lee@...nel.org,
	jejb@...ux.ibm.com,
	martin.petersen@...cle.com
Cc: linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org,
	Adaptec OEM Raid Solutions <aacraid@...rosemi.com>,
	"PMC-Sierra, Inc" <aacraid@...-sierra.com>
Subject: [PATCH 5/5] scsi: aacraid: aachba: 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
Cc: Adaptec OEM Raid Solutions <aacraid@...rosemi.com>
Cc: "PMC-Sierra, Inc" <aacraid@...-sierra.com>
Signed-off-by: Lee Jones <lee@...nel.org>
---
 drivers/scsi/aacraid/aachba.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/aacraid/aachba.c b/drivers/scsi/aacraid/aachba.c
index 70e1cac1975eb..b22857c6f3f4f 100644
--- a/drivers/scsi/aacraid/aachba.c
+++ b/drivers/scsi/aacraid/aachba.c
@@ -1099,7 +1099,7 @@ static void get_container_serial_callback(void *context, struct fib * fibptr)
 			sp[0] = INQD_PDT_DA;
 			sp[1] = scsicmd->cmnd[2];
 			sp[2] = 0;
-			sp[3] = snprintf(sp+4, sizeof(sp)-4, "%08X",
+			sp[3] = scnprintf(sp+4, sizeof(sp)-4, "%08X",
 				le32_to_cpu(get_serial_reply->uid));
 			scsi_sg_copy_from_buffer(scsicmd, sp,
 						 sizeof(sp));
@@ -1169,8 +1169,8 @@ static int setinqserial(struct aac_dev *dev, void *data, int cid)
 	/*
 	 *	This breaks array migration.
 	 */
-	return snprintf((char *)(data), sizeof(struct scsi_inq) - 4, "%08X%02X",
-			le32_to_cpu(dev->adapter_info.serial[0]), cid);
+	return scnprintf((char *)(data), sizeof(struct scsi_inq) - 4, "%08X%02X",
+			 le32_to_cpu(dev->adapter_info.serial[0]), cid);
 }
 
 static inline void set_sense(struct sense_data *sense_data, u8 sense_key,
-- 
2.43.0.275.g3460e3d667-goog