On Wed, 31 Jan 2018 12:58:56 +0100
Daniel Borkmann <dan...@iogearbox.net> wrote:
> syzkaller was able to generate the following XDP program ...
>
> (18) r0 = 0x0
> (61) r5 = *(u32 *)(r1 +12)
> (04) (u32) r0 += (u32) 0
> (95) exit
>
> ... and trigger a NULL pointer dereference in ___bpf_prog_run()
> via bpf_prog_test_run_xdp() where this was attempted to run.
>
> Reason is that recent xdp_rxq_info addition to XDP programs
> updated all drivers, but not bpf_prog_test_run_xdp(), where
> xdp_buff is set up. Thus when context rewriter does the deref
> on the netdev it's NULL at runtime. Fix it by using xdp_rxq
> from loopback dev. __netif_get_rx_queue() helper can also be
> reused in various other locations later on.
>
> Fixes: 02dd3291b2f0 ("bpf: finally expose xdp_rxq_info to XDP bpf-programs")
> Reported-by: syzbot+1eb094057b338eb1f...@syzkaller.appspotmail.com
> Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
> Cc: Jesper Dangaard Brouer <bro...@redhat.com>
Acked-by: Jesper Dangaard Brouer <bro...@redhat.com>
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
