usb: mon_stat: 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/105Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20231213164246.1021885-10-lee@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/mon/mon_stat.c

@@ -35,7 +35,7 @@ static int mon_stat_open(struct inode *inode, struct file *file)
 
 	mbus = inode->i_private;
 
-	sp->slen = snprintf(sp->str, STAT_BUF_SIZE,
+	sp->slen = scnprintf(sp->str, STAT_BUF_SIZE,
 			     "nreaders %d events %u text_lost %u\n",
 			     mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost);