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/net/bpf/test_run.c b/net/bpf/test_run.c
index a86e668..2ced486 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -151,6 +151,7 @@
{
u32 size = kattr->test.data_size_in;
u32 repeat = kattr->test.repeat;
+ struct netdev_rx_queue *rxqueue;
struct xdp_buff xdp = {};
u32 retval, duration;
void *data;
@@ -165,6 +166,9 @@
xdp.data_meta = xdp.data;
xdp.data_end = xdp.data + size;
+ rxqueue = __netif_get_rx_queue(current->nsproxy->net_ns->loopback_dev, 0);
+ xdp.rxq = &rxqueue->xdp_rxq;
+
retval = bpf_test_run(prog, &xdp, repeat, &duration);
if (xdp.data != data + XDP_PACKET_HEADROOM + NET_IP_ALIGN)
size = xdp.data_end - xdp.data;