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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: 02dd3291b2 ("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>
This commit is contained in:
Daniel Borkmann 2018-01-31 12:58:56 +01:00 committed by Alexei Starovoitov
parent 62a06994ce
commit 65073a6733
3 changed files with 24 additions and 0 deletions
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6
include/linux/netdevice.h
View File

@ -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)

4
net/bpf/test_run.c
View File

@ -151,6 +151,7 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
{
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 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
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;

14
tools/testing/selftests/bpf/test_verifier.c
View File

@ -7779,6 +7779,20 @@ static struct bpf_test tests[] = {
.errstr = "unknown opcode d7",
.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 = {