On Thu, Aug 29, 2024 at 5:45 AM Tze-nan Wu (吳澤南)
<Tze-nan.Wu@xxxxxxxxxxxx> wrote:
>
> On Fri, 2024-08-23 at 19:04 -0700, Stanislav Fomichev wrote:
> >
> > External email : Please do not click links or open attachments until
> > you have verified the sender or the content.
> > On 08/22, Alexei Starovoitov wrote:
> > > On Thu, Aug 22, 2024 at 12:02 AM Tze-nan Wu (吳澤南)
> > > <Tze-nan.Wu@xxxxxxxxxxxx> wrote:
> > > >
> > > >
> > > > BTW, If this should be handled in kernel, modification shown
> > below
> > > > could fix the issue without breaking the "static_branch" usage in
> > both
> > > > macros:
> > > >
> > > >
> > > > +++ /include/linux/bpf-cgroup.h:
> > > > -#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen)
> > > > +#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen, compat)
> > > > ({
> > > > int __ret = 0;
> > > > if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT))
> > > > copy_from_sockptr(&__ret, optlen, sizeof(int));
> > > > + else
> > > > + *compat = true;
> > > > __ret;
> > > > })
> > > >
> > > > #define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname,
> > > > optval, optlen, max_optlen, retval)
> > > > ({
> > > > int __ret = retval;
> > > > - if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT) &&
> > > > - cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))
> > > > + if (cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT))
> > > > if (!(sock)->sk_prot->bpf_bypass_getsockopt ||
> > > > ...
> > > >
> > > > +++ /net/socket.c:
> > > > int do_sock_getsockopt(struct socket *sock, bool compat, int
> > level,
> > > > {
> > > > ...
> > > > ...
> > > > + /* The meaning of `compat` variable could be changed
> > here
> > > > + * to indicate if cgroup_bpf_enabled(CGROUP_SOCK_OPS)
> > is
> > > > false.
> > > > + */
> > > > if (!compat)
> > > > - max_optlen =
> > BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);
> > > > + max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen,
> > > > &compat);
> > >
> > > This is better, but it's still quite a hack. Let's not override it.
> > > We can have another bool, but the question:
> > > do we really need BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN ?
> > > copy_from_sockptr(&__ret, optlen, sizeof(int));
> > > should be fast enough to do it unconditionally.
> > > What are we saving here?
> > >
> > > Stan ?
> >
> > Agreed, most likely nobody would notice :-)
>
> Sorry for my late reply, just have the mailer fixed.
>
> If it is feasible to make the `copy_from_sockptr` unconditionally,
> should I submit a new patch that resolve the issue by removing
> `BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN`? Patch A shown as below.
>
> +++ /net/socket.c:
> int do_sock_getsockopt(...)
> {
> - int max_optlen __maybe_unused;
> + int max_optlen __maybe_unused = 0;
> const struct proto_ops *ops;
> int err;
> ...
> ...
> if (!compat) <== wonder if we should keep the condition here?
> - max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen);
> + copy_from_sockptr(&max_optlen, optlen, sizeof(int));
This one.
And delete the macro from bpf-cgroup.h
