patch "usb: host: max3421-hcd: Replace snprintf() with the safer scnprintf()" added to usb-testing

[gregkh at linuxfoundation.org]

This is a note to let you know that I've just added the patch titled

    usb: host: max3421-hcd: Replace snprintf() with the safer scnprintf()

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the usb-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


>From a6eef67cdb84e06112fc29176d6c6061d3ea8d79 Mon Sep 17 00:00:00 2001
From: Lee Jones <lee at kernel.org>
Date: Wed, 13 Dec 2023 16:42:36 +0000
Subject: 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 at microchip.com>
Cc: Nicolas Ferre <nicolas.ferre at microchip.com>
Cc: Alexandre Belloni <alexandre.belloni at bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea at tuxon.dev>
Cc:  <linux-arm-kernel at lists.infradead.org>
Signed-off-by: Lee Jones <lee at kernel.org>
Link: https://lore.kernel.org/r/20231213164246.1021885-8-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/usb/host/max3421-hcd.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c
index d152d72de126..9fe4f48b1898 100644
--- a/drivers/usb/host/max3421-hcd.c
+++ b/drivers/usb/host/max3421-hcd.c
@@ -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,
-				       usb_pipetype(urb->pipe),
-				       usb_urb_dir_in(urb) ? "IN" : "OUT",
-				       urb->actual_length,
-				       urb->transfer_buffer_length);
-			if (ret < 0 || ret >= end - dp)
+			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 == 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",
-						   max3421_hcd->err_stat[i]);
-				if (ret < 0 || ret >= end - dp)
+				int ret = scnprintf(dp, end - dp, " %lu",
+						    max3421_hcd->err_stat[i]);
+				if (ret == end - dp - 1)
 					break;	/* error or buffer full */
 				dp += ret;
 			}
-- 
2.43.0