Commit a6eef67c authored Dec 13, 2023 by Lee Jones Committed by Greg Kroah-Hartman Dec 15, 2023

usb: host: max3421-hcd: 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/20231213164246.1021885-8-lee@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 01dc7f7c

drivers/usb/host/max3421-hcd.c

+9 −9

Original line number	Diff line number	Diff line
		@@ -1158,12 +1158,12 @@ dump_eps(struct usb_hcd *hcd)
		end = dp + sizeof(ubuf);
		*dp = '\0';
		list_for_each_entry(urb, &ep->urb_list, urb_list) {
		ret = snprintf(dp, end - dp, " %p(%d.%s %d/%d)", urb,
		ret = scnprintf(dp, end - dp, " %p(%d.%s %d/%d)", urb,
		usb_pipetype(urb->pipe),
		usb_urb_dir_in(urb) ? "IN" : "OUT",
		urb->actual_length,
		urb->transfer_buffer_length);
		if (ret < 0 \|\| ret >= end - dp)
		if (ret == end - dp - 1)
		break; /* error or buffer full */
		dp += ret;
		}
		@@ -1255,9 +1255,9 @@ max3421_handle_irqs(struct usb_hcd *hcd)
		end = sbuf + sizeof(sbuf);
		*dp = '\0';
		for (i = 0; i < 16; ++i) {
		int ret = snprintf(dp, end - dp, " %lu",
		int ret = scnprintf(dp, end - dp, " %lu",
		max3421_hcd->err_stat[i]);
		if (ret < 0 \|\| ret >= end - dp)
		if (ret == end - dp - 1)
		break; /* error or buffer full */
		dp += ret;
		}