usb: gadget: uvc: 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: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Scally <dan.scally@ideasonboard.com>
Cc: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20231213164246.1021885-5-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
index 9bf0e985acfab531dfe70989a7000c1a0fe09caf..7e704b2bcfd1ce5a2c28a4f318fca6633a7072f8 100644 (file)
--- a/drivers/usb/gadget/function/uvc_configfs.c
+++ b/drivers/usb/gadget/function/uvc_configfs.c
@@ -3414,7 +3414,7 @@ static ssize_t f_uvc_opts_string_##cname##_show(struct config_item *item,\
        int result;                                                     \
                                                                        \
        mutex_lock(&opts->lock);                                        \
-       result = snprintf(page, sizeof(opts->aname), "%s", opts->aname);\
+       result = scnprintf(page, sizeof(opts->aname), "%s", opts->aname);\
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \