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>
}
#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)
{
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;
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;
.result = REJECT,
},
{
+ "XDP, using ifindex from netdev",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
+ offsetof(struct xdp_md, ingress_ifindex)),
+ BPF_JMP_IMM(BPF_JLT, BPF_REG_2, 1, 1),
+ BPF_MOV64_IMM(BPF_REG_0, 1),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_XDP,
+ .retval = 1,
+ },
+ {
"meta access, test1",
.insns = {
BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,