scsi: ipr: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the actual
output size, the succeeding calls may go beyond the given buffer limit.
Fix it by replacing with scnprintf().

Link: https://lore.kernel.org/r/20200315094241.9086-6-tiwai@suse.de
Cc: "James E . J . Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>
Cc: Brian King <brking@us.ibm.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ipr.c

@@ -1299,9 +1299,9 @@ static char *__ipr_format_res_path(u8 *res_path, char *buffer, int len)
 	char *p = buffer;
 
 	*p = '\0';
-	p += snprintf(p, buffer + len - p, "%02X", res_path[0]);
+	p += scnprintf(p, buffer + len - p, "%02X", res_path[0]);
 	for (i = 1; res_path[i] != 0xff && ((i * 3) < len); i++)
-		p += snprintf(p, buffer + len - p, "-%02X", res_path[i]);
+		p += scnprintf(p, buffer + len - p, "-%02X", res_path[i]);
 
 	return buffer;
 }
@@ -1322,7 +1322,7 @@ static char *ipr_format_res_path(struct ipr_ioa_cfg *ioa_cfg,
 	char *p = buffer;
 
 	*p = '\0';
-	p += snprintf(p, buffer + len - p, "%d/", ioa_cfg->host->host_no);
+	p += scnprintf(p, buffer + len - p, "%d/", ioa_cfg->host->host_no);
 	__ipr_format_res_path(res_path, p, len - (buffer - p));
 	return buffer;
 }