On Fri, Jun 9, 2023 at 12:41 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> On Fri, Jun 09, 2023 at 11:13:03AM -0400, Xin Long wrote:
> > This one looks good to me.
> >
> > But for the patch 1/2 (somehow it doesn't show up in my mailbox):
> >
> > default:
> > pr_err("impossible disposition %d in state %d, event_type %d, event_id %d\n",
> > status, state, event_type, subtype.chunk);
> > - BUG();
> > + error = status;
> > + if (error >= 0)
> > + error = -EINVAL;
> > + WARN_ON_ONCE(1);
> >
> > I think from the sctp_do_sm() perspective, it expects the state_fn
> > status only from
> > enum sctp_disposition. It is a BUG to receive any other values and
> > must be fixed,
> > as you did in 2/2. It does the same thing as other functions in SCTP code, like
> > sctp_sf_eat_data_*(), sctp_retransmit() etc.
>
> It is a bug, sure. And after my patch is applied it will still trigger
> a stack trace. But we should only call the actual BUG() function
> in order to prevent filesystem corruption or a privilege escalation or
> something along those lines.
Hi, Dan,
Sorry, I'm not sure about this.
Look at the places where it's using BUG(), it's not exactly the case, like
in ping_err() or ping_common_sendmsg(), BUG() are used more for
unexpected cases, which don't cause any filesystem corruption or a
privilege escalation.
You may also check more others under net/*.
>
> Calling BUG() makes the system unusable so it makes bugs harder to
> debug. This is even mentioned in checkpatch.pl "Do not crash the kernel
> unless it is absolutely unavoidable--use WARN_ON_ONCE() plus recovery
> code (if feasible) instead of BUG() or variants".
>
"absolutely unavoidable", I think in a module, if it gets a case that is not
expected at all, and the consequence (it may cause or has caused) is
unsure, WARN_ON_ONCE() is not enough.
Thanks.
