bpf: fix null pointer deref in bpf_prog_test_run_xdp
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+1eb094057b338eb1fc00@syzkaller.appspotmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4c77f39..5eef6c8 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3228,6 +3228,12 @@ static inline int netif_set_real_num_rx_queues(struct net_device *dev,
}
#endif
+static inline struct netdev_rx_queue *
+__netif_get_rx_queue(struct net_device *dev, unsigned int rxq)
+{
+ return dev->_rx + rxq;
+}
+
#ifdef CONFIG_SYSFS
static inline unsigned int get_netdev_rx_queue_index(
struct netdev_rx_queue *queue)