From: Jiayuan Chen bond_rr_gen_slave_id() dereferences bond->rr_tx_counter without a NULL check. rr_tx_counter is a per-CPU counter only allocated in bond_open() when the bond mode is round-robin. If the bond device was never brought up, rr_tx_counter remains NULL, causing a null-ptr-deref. The XDP redirect path can reach this code even when the bond is not up: bpf_master_redirect_enabled_key is a global static key, so when any bond device has native XDP attached, the XDP_TX -> xdp_master_redirect() interception is enabled for all bond slaves system-wide. This allows the path xdp_master_redirect() -> bond_xdp_get_xmit_slave() -> bond_xdp_xmit_roundrobin_slave_get() -> bond_rr_gen_slave_id() to be reached on a bond that was never opened. The normal TX path (bond_xmit_roundrobin) is not affected because TX requires the bond to be UP, which guarantees rr_tx_counter is allocated. However, bond_xmit_get_slave() (ndo_get_xmit_slave) has the same code pattern via bond_xmit_roundrobin_slave_get() and could theoretically hit the same issue. Fix this by introducing bond_create_init() to allocate rr_tx_counter unconditionally at device creation time. It is called from both bond_create() and bond_newlink() before register_netdevice(), and returns -ENOMEM on failure so callers can propagate the error cleanly. bond_setup() is not suitable for this allocation as it is a void callback with no error return path. The conditional allocation in bond_open() is removed. Since bond_destructor() already unconditionally calls free_percpu(bond->rr_tx_counter), the lifecycle is clean: allocate at creation, free at destruction. Fixes: 879af96ffd72 ("net, core: Add support for XDP redirection to slave device") Reported-by: syzbot+80e046b8da2820b6ba73@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/698f84c6.a70a0220.2c38d7.00cc.GAE@google.com/T/ Signed-off-by: Jiayuan Chen --- drivers/net/bonding/bond_main.c | 18 ++++++++++++------ drivers/net/bonding/bond_netlink.c | 4 ++++ include/net/bonding.h | 1 + 3 files changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 78cff904cdc3..806034dc301f 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -4273,18 +4273,18 @@ void bond_work_cancel_all(struct bonding *bond) cancel_delayed_work_sync(&bond->peer_notify_work); } +int bond_create_init(struct bonding *bond) +{ + bond->rr_tx_counter = alloc_percpu(u32); + return bond->rr_tx_counter ? 0 : -ENOMEM; +} + static int bond_open(struct net_device *bond_dev) { struct bonding *bond = netdev_priv(bond_dev); struct list_head *iter; struct slave *slave; - if (BOND_MODE(bond) == BOND_MODE_ROUNDROBIN && !bond->rr_tx_counter) { - bond->rr_tx_counter = alloc_percpu(u32); - if (!bond->rr_tx_counter) - return -ENOMEM; - } - /* reset slave->backup and slave->inactive */ if (bond_has_slaves(bond)) { bond_for_each_slave(bond, slave, iter) { @@ -6458,6 +6458,12 @@ int bond_create(struct net *net, const char *name) dev_net_set(bond_dev, net); bond_dev->rtnl_link_ops = &bond_link_ops; + res = bond_create_init(bond); + if (res) { + free_netdev(bond_dev); + goto out; + } + res = register_netdevice(bond_dev); if (res < 0) { free_netdev(bond_dev); diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c index 286f11c517f7..91595df85f06 100644 --- a/drivers/net/bonding/bond_netlink.c +++ b/drivers/net/bonding/bond_netlink.c @@ -598,6 +598,10 @@ static int bond_newlink(struct net_device *bond_dev, struct nlattr **tb = params->tb; int err; + err = bond_create_init(bond); + if (err) + return err; + err = register_netdevice(bond_dev); if (err) return err; diff --git a/include/net/bonding.h b/include/net/bonding.h index 4ad5521e7731..dac4725f3ac0 100644 --- a/include/net/bonding.h +++ b/include/net/bonding.h @@ -714,6 +714,7 @@ void bond_slave_arr_work_rearm(struct bonding *bond, unsigned long delay); void bond_peer_notify_work_rearm(struct bonding *bond, unsigned long delay); void bond_work_init_all(struct bonding *bond); void bond_work_cancel_all(struct bonding *bond); +int bond_create_init(struct bonding *bond); #ifdef CONFIG_PROC_FS void bond_create_proc_entry(struct bonding *bond); -- 2.43.0 From: Jiayuan Chen Add a selftest that reproduces the null-ptr-deref in bond_rr_gen_slave_id() when XDP redirect targets a bond device in round-robin mode that was never brought up. The test verifies the fix by ensuring no crash occurs. Test setup: - bond0: active-backup mode, UP, with native XDP (enables bpf_master_redirect_enabled_key globally) - bond1: round-robin mode, never UP - veth1: slave of bond1, with generic XDP (XDP_TX) - BPF_PROG_TEST_RUN with live frames triggers the redirect path Signed-off-by: Jiayuan Chen --- .../selftests/bpf/prog_tests/xdp_bonding.c | 101 +++++++++++++++++- 1 file changed, 99 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c b/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c index fb952703653e..a5b15e464018 100644 --- a/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c +++ b/tools/testing/selftests/bpf/prog_tests/xdp_bonding.c @@ -191,13 +191,18 @@ static int bonding_setup(struct skeletons *skeletons, int mode, int xmit_policy, return -1; } -static void bonding_cleanup(struct skeletons *skeletons) +static void link_cleanup(struct skeletons *skeletons) { - restore_root_netns(); while (skeletons->nlinks) { skeletons->nlinks--; bpf_link__destroy(skeletons->links[skeletons->nlinks]); } +} + +static void bonding_cleanup(struct skeletons *skeletons) +{ + restore_root_netns(); + link_cleanup(skeletons); ASSERT_OK(system("ip link delete bond1"), "delete bond1"); ASSERT_OK(system("ip link delete veth1_1"), "delete veth1_1"); ASSERT_OK(system("ip link delete veth1_2"), "delete veth1_2"); @@ -493,6 +498,95 @@ static void test_xdp_bonding_nested(struct skeletons *skeletons) system("ip link del bond_nest2"); } +/* + * Test that XDP redirect via xdp_master_redirect() does not crash when + * the bond master device is not up. When bond is in round-robin mode but + * never opened, rr_tx_counter is NULL. + */ +static void test_xdp_bonding_redirect_no_up(struct skeletons *skeletons) +{ + struct nstoken *nstoken = NULL; + int xdp_pass_fd, xdp_tx_fd; + int veth1_ifindex; + int err; + char pkt[ETH_HLEN + 1]; + struct xdp_md ctx_in = {}; + + DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts, + .data_in = &pkt, + .data_size_in = sizeof(pkt), + .ctx_in = &ctx_in, + .ctx_size_in = sizeof(ctx_in), + .flags = BPF_F_TEST_XDP_LIVE_FRAMES, + .repeat = 1, + .batch_size = 1, + ); + + /* We can't use bonding_setup() because bond will be active */ + SYS(out, "ip netns add ns_rr_no_up"); + nstoken = open_netns("ns_rr_no_up"); + if (!ASSERT_OK_PTR(nstoken, "open ns_rr_no_up")) + goto out; + + /* bond0: active-backup, UP with slave veth0. + * Attaching native XDP to bond0 enables bpf_master_redirect_enabled_key + * globally. + */ + SYS(out, "ip link add bond0 type bond mode active-backup"); + SYS(out, "ip link add veth0 type veth peer name veth0p"); + SYS(out, "ip link set veth0 master bond0"); + SYS(out, "ip link set bond0 up"); + SYS(out, "ip link set veth0p up"); + + /* bond1: round-robin, never UP -> rr_tx_counter stays NULL */ + SYS(out, "ip link add bond1 type bond mode balance-rr"); + SYS(out, "ip link add veth1 type veth peer name veth1p"); + SYS(out, "ip link set veth1 master bond1"); + + veth1_ifindex = if_nametoindex("veth1"); + if (!ASSERT_GT(veth1_ifindex, 0, "veth1_ifindex")) + goto out; + + /* Attach native XDP to bond0 -> enables global redirect key */ + if (xdp_attach(skeletons, skeletons->xdp_tx->progs.xdp_tx, "bond0")) + goto out; + + /* Attach generic XDP (XDP_TX) to veth1. + * When packets arrive at veth1 via netif_receive_skb, do_xdp_generic() + * runs this program. XDP_TX + bond slave triggers xdp_master_redirect(). + */ + xdp_tx_fd = bpf_program__fd(skeletons->xdp_tx->progs.xdp_tx); + if (!ASSERT_GE(xdp_tx_fd, 0, "xdp_tx prog_fd")) + goto out; + + err = bpf_xdp_attach(veth1_ifindex, xdp_tx_fd, + XDP_FLAGS_SKB_MODE, NULL); + if (!ASSERT_OK(err, "attach generic XDP to veth1")) + goto out; + + /* Run BPF_PROG_TEST_RUN with XDP_PASS live frames on veth1. + * XDP_PASS frames become SKBs with skb->dev = veth1, entering + * netif_receive_skb -> do_xdp_generic -> xdp_master_redirect. + * Without the fix, bond_rr_gen_slave_id() dereferences NULL + * rr_tx_counter and crashes. + */ + xdp_pass_fd = bpf_program__fd(skeletons->xdp_dummy->progs.xdp_dummy_prog); + if (!ASSERT_GE(xdp_pass_fd, 0, "xdp_pass prog_fd")) + goto out; + + memset(pkt, 0, sizeof(pkt)); + ctx_in.data_end = sizeof(pkt); + ctx_in.ingress_ifindex = veth1_ifindex; + + err = bpf_prog_test_run_opts(xdp_pass_fd, &opts); + ASSERT_OK(err, "xdp_pass test_run should not crash"); + +out: + link_cleanup(skeletons); + close_netns(nstoken); + SYS_NOFAIL("ip netns del ns_rr_no_up"); +} + static void test_xdp_bonding_features(struct skeletons *skeletons) { LIBBPF_OPTS(bpf_xdp_query_opts, query_opts); @@ -680,6 +774,9 @@ void serial_test_xdp_bonding(void) if (test__start_subtest("xdp_bonding_redirect_multi")) test_xdp_bonding_redirect_multi(&skeletons); + if (test__start_subtest("xdp_bonding_redirect_no_up")) + test_xdp_bonding_redirect_no_up(&skeletons); + out: xdp_dummy__destroy(skeletons.xdp_dummy); xdp_tx__destroy(skeletons.xdp_tx); -- 2.43.0