usb: gadget: udc: atmel: 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: Cristian Birsan <cristian.birsan@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc:  <linux-arm-kernel@lists.infradead.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20231213164246.1021885-6-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/udc/atmel_usba_udc.c b/drivers/usb/gadget/udc/atmel_usba_udc.c
index 02b1bef5e22e2e5c22c03630277c0193ff58aad1..b76885d78e8a780b9b57cf37b4163e0242ca08aa 100644 (file)
--- a/drivers/usb/gadget/udc/atmel_usba_udc.c
+++ b/drivers/usb/gadget/udc/atmel_usba_udc.c
@@ -94,7 +94,7 @@ static ssize_t queue_dbg_read(struct file *file, char __user *buf,
 
        inode_lock(file_inode(file));
        list_for_each_entry_safe(req, tmp_req, queue, queue) {
-               len = snprintf(tmpbuf, sizeof(tmpbuf),
+               len = scnprintf(tmpbuf, sizeof(tmpbuf),
                                "%8p %08x %c%c%c %5d %c%c%c\n",
                                req->req.buf, req->req.length,
                                req->req.no_interrupt ? 'i' : 'I',
@@ -104,7 +104,6 @@ static ssize_t queue_dbg_read(struct file *file, char __user *buf,
                                req->submitted ? 'F' : 'f',
                                req->using_dma ? 'D' : 'd',
                                req->last_transaction ? 'L' : 'l');
-               len = min(len, sizeof(tmpbuf));
                if (len > nbytes)
                        break;