usb: mon_text: 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/20231213164246.1021885-11-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/mon/mon_text.c b/drivers/usb/mon/mon_text.c
index 39cb141646526dbc362e71890b6494d677f84f62..2fe9b95bac1d57727a431a96f10c332f95fdb763 100644 (file)
--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -352,7 +352,7 @@ static int mon_text_open(struct inode *inode, struct file *file)
        rp->r.rnf_error = mon_text_error;
        rp->r.rnf_complete = mon_text_complete;
 
-       snprintf(rp->slab_name, SLAB_NAME_SZ, "mon_text_%p", rp);
+       scnprintf(rp->slab_name, SLAB_NAME_SZ, "mon_text_%p", rp);
        rp->e_slab = kmem_cache_create(rp->slab_name,
            sizeof(struct mon_event_text), sizeof(long), 0,
            mon_text_ctor);
@@ -700,46 +700,28 @@ static const struct file_operations mon_fops_text_u = {
 
 int mon_text_add(struct mon_bus *mbus, const struct usb_bus *ubus)
 {
-       enum { NAMESZ = 10 };
+       enum { NAMESZ = 12 };
        char name[NAMESZ];
        int busnum = ubus? ubus->busnum: 0;
-       int rc;
 
        if (mon_dir == NULL)
                return 0;
 
        if (ubus != NULL) {
-               rc = snprintf(name, NAMESZ, "%dt", busnum);
-               if (rc <= 0 || rc >= NAMESZ)
-                       goto err_print_t;
+               scnprintf(name, NAMESZ, "%dt", busnum);
                mbus->dent_t = debugfs_create_file(name, 0600, mon_dir, mbus,
                                                             &mon_fops_text_t);
        }
 
-       rc = snprintf(name, NAMESZ, "%du", busnum);
-       if (rc <= 0 || rc >= NAMESZ)
-               goto err_print_u;
+       scnprintf(name, NAMESZ, "%du", busnum);
        mbus->dent_u = debugfs_create_file(name, 0600, mon_dir, mbus,
                                           &mon_fops_text_u);
 
-       rc = snprintf(name, NAMESZ, "%ds", busnum);
-       if (rc <= 0 || rc >= NAMESZ)
-               goto err_print_s;
+       scnprintf(name, NAMESZ, "%ds", busnum);
        mbus->dent_s = debugfs_create_file(name, 0600, mon_dir, mbus,
                                           &mon_fops_stat);
 
        return 1;
-
-err_print_s:
-       debugfs_remove(mbus->dent_u);
-       mbus->dent_u = NULL;
-err_print_u:
-       if (ubus != NULL) {
-               debugfs_remove(mbus->dent_t);
-               mbus->dent_t = NULL;
-       }
-err_print_t:
-       return 0;
 }
 
 void mon_text_del(struct mon_bus *mbus)