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

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-next 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 also be merged in the next major kernel release during the merge window.

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

From a6eef67cdb84e06112fc29176d6c6061d3ea8d79 Mon Sep 17 00:00:00 2001
From: Lee Jones <[email protected]>
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.

---
 drivers/usb/host/max3421-hcd.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

index d152d72de126..9fe4f48b1898 100644
@@ -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



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