Re: [PATCHv3] dvb: usb: fix use after free in dvb_usb_device_exit

[Mauro Carvalho Chehab <mchehab@kernel.org>]

Em Tue, 30 Apr 2019 14:16:07 +0200
Oliver Neukum <oneukum@suse.com> escreveu:

> dvb_usb_device_exit() frees and uses the device name in that order
> Fix by storing the name in a buffer before freeing it
> 
> v2: fixed style issues
> v3: strscpy used and variable names changed
> 
> Signed-off-by: Oliver Neukum <oneukum@suse.com>
> Reported-by: syzbot+26ec41e9f788b3eba396@syzkaller.appspotmail.com
> ---
>  drivers/media/usb/dvb-usb/dvb-usb-init.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
> index 99951e02a880..48d17736db5d 100644
> --- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
> +++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
> @@ -287,12 +287,15 @@ EXPORT_SYMBOL(dvb_usb_device_init);
>  void dvb_usb_device_exit(struct usb_interface *intf)
>  {
>  	struct dvb_usb_device *d = usb_get_intfdata(intf);
> -	const char *name = "generic DVB-USB module";
> +	const char *default_name = "generic DVB-USB module";
> +	char name[40];
>  
>  	usb_set_intfdata(intf, NULL);
>  	if (d != NULL && d->desc != NULL) {
> -		name = d->desc->name;
> +		strscpy(name, d->desc->name, sizeof(name));
>  		dvb_usb_exit(d);
> +	} else {
> +		memcpy(name, default_name, sizeof(name));

Please use strscpy() here too, as we're using it everywhere 
when a string requires copy inside media.

>  	}
>  	info("%s successfully deinitialized and disconnected.", name);
>  



Thanks,
Mauro