[PATCH bpf] bpf: fix null pointer deref in bpf_prog_test_run_xdp
From: Daniel Borkmann <daniel@iogearbox.net>
Date: 2018-01-31 00:31:19
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 <redacted>
---
[ Note: Needs to wait till Linus pulled Dave's net-next so
the affected commit lands in bpf tree. ]
include/linux/netdevice.h | 6 ++++++
net/bpf/test_run.c | 4 ++++
tools/testing/selftests/bpf/test_verifier.c | 14 ++++++++++++++
3 files changed, 24 insertions(+)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cd46d3d..9630f4e 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)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index a86e668..47cd0b7 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c@@ -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;
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 697bd83..c0f16e9 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c@@ -7780,6 +7780,20 @@ static struct bpf_test tests[] = { .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,
--
2.9.5