netdev - Re: [PATCH net] rtnetlink: not allow dev gro_max_size to exceed GRO_MAX

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Message-ID: <CADvbK_eujS_Kg3FenuAhOMv+Xga92H9o92LC3Lw=f+7NYdxRoA@mail.gmail.com>
Date: Sun, 21 May 2023 19:27:10 -0400
From: Xin Long <lucien.xin@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Stephen Hemminger <stephen@...workplumber.org>, network dev <netdev@...r.kernel.org>, 
	davem@...emloft.net, kuba@...nel.org, Paolo Abeni <pabeni@...hat.com>, 
	Alexander Duyck <alexanderduyck@...com>
Subject: Re: [PATCH net] rtnetlink: not allow dev gro_max_size to exceed GRO_MAX_SIZE

On Sun, May 21, 2023 at 1:25 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Fri, May 19, 2023 at 10:43 PM Stephen Hemminger
> <stephen@...workplumber.org> wrote:
> >
> > On Fri, 19 May 2023 13:16:08 -0400
> > Xin Long <lucien.xin@...il.com> wrote:
> >
> > > In commit 0fe79f28bfaf ("net: allow gro_max_size to exceed 65536"),
> > > it limited GRO_MAX_SIZE to (8 * 65535) to avoid overflows, but also
> > > deleted the check of GRO_MAX_SIZE when setting the dev gro_max_size.
> > >
> > > Currently, dev gro_max_size can be set up to U32_MAX (0xFFFFFFFF),
> > > and GRO_MAX_SIZE is not even used anywhere.
> > >
> > > This patch brings back the GRO_MAX_SIZE check when setting dev
> > > gro_max_size/gro_ipv4_max_size by users.
> > >
> > > Fixes: 0fe79f28bfaf ("net: allow gro_max_size to exceed 65536")
> > > Reported-by: Xiumei Mu <xmu@...hat.com>
> > > Signed-off-by: Xin Long <lucien.xin@...il.com>
> > > ---
> > >  net/core/rtnetlink.c | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > >
> > > diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> > > index 653901a1bf75..59b24b184cb0 100644
> > > --- a/net/core/rtnetlink.c
> > > +++ b/net/core/rtnetlink.c
> > > @@ -2886,6 +2886,11 @@ static int do_setlink(const struct sk_buff *skb,
> > >       if (tb[IFLA_GRO_MAX_SIZE]) {
> > >               u32 gro_max_size = nla_get_u32(tb[IFLA_GRO_MAX_SIZE]);
> > >
> > > +             if (gro_max_size > GRO_MAX_SIZE) {
> > > +                     err = -EINVAL;
> > > +                     goto errout;
> > > +             }
> > > +
> >
> > Please add extack messages so the error can be reported better.
>
> Also, what is the reason for not changing rtnl_create_link() ?
Good catch!

Not only GRO_MAX_SIZE, all tb[IFLA_GSO/GRO_*] checks should be moved
to validate_linkmsg(), with extra added for sure. Otherwise:

# ip link add dummy1 gso_max_size 4294967295 gro_max_size 4294967295
gso_ipv4_max_size 4294967295 gro_ipv4_max_size 4294967295 type dummy
# ip -d link show dummy1
6: dummy1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode
DEFAULT group default qlen 1000
    link/ether ba:cd:f2:8d:84:9b brd ff:ff:ff:ff:ff:ff promiscuity 0
allmulti 0 minmtu 0 maxmtu 0
    dummy addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size
4294967295 gso_max_segs 65535 tso_max_size 65536 tso_max_segs 65535
gro_max_size 4294967295 gso_ipv4_max_size 4294967295 gro_ipv4_max_size
4294967295

Also, I might move validate_linkmsg() from do_setlink() to its caller,
to avoid validate_linkmsg() being called twice in the path of:
__rtnl_newlink() -> do_setlink().

Thanks.