netdev - Re: [PATCH bpf] xdp: use trusted arguments in XDP hints kfuncs

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Date: Tue, 11 Jul 2023 20:06:38 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Stanislav Fomichev <sdf@...gle.com>
Cc: Jesper Dangaard Brouer <jbrouer@...hat.com>, Larysa Zaremba <larysa.zaremba@...el.com>, 
	bpf <bpf@...r.kernel.org>, Jesper Dangaard Brouer <brouer@...hat.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
	Martin KaFai Lau <martin.lau@...nel.org>, Network Development <netdev@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf] xdp: use trusted arguments in XDP hints kfuncs

On Tue, Jul 11, 2023 at 10:00 AM Stanislav Fomichev <sdf@...gle.com> wrote:
>
> On Tue, Jul 11, 2023 at 7:21 AM Jesper Dangaard Brouer
> <jbrouer@...hat.com> wrote:
> >
> >
> > On 11/07/2023 12.59, Larysa Zaremba wrote:
> > > Currently, verifier does not reject XDP programs that pass NULL pointer to
> > > hints functions. At the same time, this case is not handled in any driver
> > > implementation (including veth). For example, changing
> > >
> > > bpf_xdp_metadata_rx_timestamp(ctx, &timestamp);
> > >
> > > to
> > >
> > > bpf_xdp_metadata_rx_timestamp(ctx, NULL);
> > >
> > > in xdp_metadata test successfully crashes the system.
> > >
> > > Add KF_TRUSTED_ARGS flag to hints kfunc definitions, so driver code
> > > does not have to worry about getting invalid pointers.
> > >
> >
> > Looks good to me, assuming this means verifier will reject BPF-prog's
> > supplying NULL.
> >
> > Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>
> >
> > > Fixes: 3d76a4d3d4e5 ("bpf: XDP metadata RX kfuncs")
> > > Reported-by: Stanislav Fomichev <sdf@...gle.com>
> > > Closes: https://lore.kernel.org/bpf/ZKWo0BbpLfkZHbyE@google.com/
> > > Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
>
> Acked-by: Stanislav Fomichev <sdf@...gle.com>
>
> Thank you for the fix!

Applied. Thanks