Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value

[Christophe Leroy <christophe.leroy@xxxxxxxxxx>]

Le 13/05/2021 à 12:03, Juergen Gross a écrit :
> Xen frontends shouldn't BUG() in case of illegal data received from
> their backends. So replace the BUG_ON()s when reading illegal data from
> the ring page with negative return values.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>   drivers/tty/hvc/hvc_xen.c | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> index 92c9a476defc..30d7ffb1e04c 100644
> --- a/drivers/tty/hvc/hvc_xen.c
> +++ b/drivers/tty/hvc/hvc_xen.c
> @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons,
>         cons = intf->out_cons;
>         prod = intf->out_prod;
>         mb();                   /* update queue values before going on */
> +
> +       if (WARN_ONCE((prod - cons) > sizeof(intf->out),
> +                     "Illegal ring page indices"))
> +               return -EINVAL;
> +
>         BUG_ON((prod - cons) > sizeof(intf->out));
Why keep the BUG_ON() ?


>   
>   	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
> @@ -114,7 +119,10 @@ static int domU_write_console(uint32_t vtermno, const char 
> *data, int len)
>          */
>         while (len) {
>                 int sent = __write_console(cons, data, len);
> -               
> +
> +               if (sent < 0)
> +                       return sent;
> +
>                 data += sent;
>                 len -= sent;
>   
> @@ -138,7 +146,10 @@ static int domU_read_console(uint32_t vtermno, char *buf, int len)
>         cons = intf->in_cons;
>         prod = intf->in_prod;
>         mb();                   /* get pointers before reading ring */
> -       BUG_ON((prod - cons) > sizeof(intf->in));
> +
> +       if (WARN_ONCE((prod - cons) > sizeof(intf->in),
> +                     "Illegal ring page indices"))
> +               return -EINVAL;
>   
>   	while (cons != prod && recv < len)
>                 buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];