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

diff --git a/drivers/usb/mon/mon_stat.c b/drivers/usb/mon/mon_stat.c
index 98ab0cc473d675592ff54ceea1ae99d408eb446e..3c23805ab1a44441ec92c3bacd1bd49ee0871ccf 100644 (file)
--- a/drivers/usb/mon/mon_stat.c
+++ b/drivers/usb/mon/mon_stat.c
@@ -35,9 +35,9 @@ static int mon_stat_open(struct inode *inode, struct file *file)
 
        mbus = inode->i_private;
 
-       sp->slen = snprintf(sp->str, STAT_BUF_SIZE,
-           "nreaders %d events %u text_lost %u\n",
-           mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost);
+       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);
 
        file->private_data = sp;
        return 0;