kernel/linux.git/drivers/net/bonding, branch v6.18.40

bonding: 3ad: fix mux port state on oper down

2026-07-24T14:16:07+00:00

[ Upstream commit 807afc7544b865d4d09068a415fd5b71bf5665cc ] When the bonding interface has carrier down due to the absence of usable slaves and a slave transitions from down to up, the bonding interface briefly goes carrier up, then down again, and finally up once LACP negotiates collecting and distributing on the port. When lacp_strict mode is on, the interface should not transition to carrier up until LACP negotiation is complete. This happens because the actor and partner port states remain in Collecting_Distributing when the port goes down. When the port comes back up, it temporarily remains in this state until LACP renegotiation occurs. Previously this was mostly cosmetic, but since the bonding carrier state may depend on the LACP negotiation state, it causes the interface to flap. According to IEEE 802.3ad-2000 and IEEE 802.1ax-2014, Collecting and Distributing should be reset when a port goes down: - In the Receive state machine, port_enabled == FALSE causes a transition to the PORT_DISABLED state, which is expected to clear Partner_Oper_Port_State.Synchronization. - In the Mux state machine, Partner_Oper_Port_State.Synchronization == FALSE causes a transition to the ATTACHED state, which disables Collecting and Distributing. However, Partner_Oper_Port_State.Synchronization is not cleared in the PORT_DISABLED state. Clear Partner_Oper_Port_State.Synchronization in the Receive PORT_DISABLED state. Fixes: 655f8919d549 ("bonding: add min links parameter to 802.3ad") Signed-off-by: Louis Scalbert Acked-by: Jay Vosburgh Link: https://patch.msgid.link/20260603150331.1919611-6-louis.scalbert@6wind.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bonding: 3ad: fix carrier when no usable slaves

2026-07-24T14:16:07+00:00

[ Upstream commit 0bd695db23c6262e9cb980017a6273925172ec5b ] Apply the "lacp_strict" configuration from the previous commit. "lacp_strict" mode "on" asserts that the bonding master carrier is up only when at least 'min_links' slaves are in the Collecting_Distributing state. Fixes: 655f8919d549 ("bonding: add min links parameter to 802.3ad") Signed-off-by: Louis Scalbert Acked-by: Jay Vosburgh Link: https://patch.msgid.link/20260603150331.1919611-5-louis.scalbert@6wind.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bonding: 3ad: add lacp_strict configuration knob

2026-07-24T14:16:07+00:00

[ Upstream commit 32b0b8953343eaceaa816a9ead3b6bb66355c64e ] When an 802.3ad (LACP) bonding interface has no slaves in the collecting/distributing state, the bonding master still reports carrier as up as long as at least 'min_links' slaves have carrier. In this situation, only one slave is effectively used for TX/RX, while traffic received on other slaves is dropped. Upper-layer daemons therefore consider the interface operational, even though traffic may be blackholed if the lack of LACP negotiation means the partner is not ready to deal with traffic. Introduce a configuration knob to control this behavior. It allows the bonding master to assert carrier only when at least 'min_links' slaves are in Collecting_Distributing state. The default mode preserves the existing behavior. This patch only introduces the knob; its behavior is implemented in the subsequent commit. Fixes: 655f8919d549 ("bonding: add min links parameter to 802.3ad") Signed-off-by: Louis Scalbert Acked-by: Jay Vosburgh Link: https://patch.msgid.link/20260603150331.1919611-4-louis.scalbert@6wind.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: bonding: fix NULL pointer dereference in bond_do_ioctl()

2026-06-19T11:44:09+00:00

commit a764b0e8317a863006e05732e1aefe821b9d8c2d upstream. In bond_do_ioctl(), slave_dev is obtained via __dev_get_by_name() which can return NULL if the requested interface name does not exist. However, the subsequent slave_dbg() call is placed before the NULL check: slave_dev = __dev_get_by_name(net, ifr->ifr_slave); slave_dbg(bond_dev, slave_dev, "slave_dev=%p:\n", slave_dev); //here if (!slave_dev) return -ENODEV; The slave_dbg() macro expands to netdev_dbg(bond_dev, "(slave %s): " fmt, (slave_dev)->name, ...) which unconditionally dereferences slave_dev->name before the NULL check is performed. This results in a NULL pointer dereference kernel oops when a user calls bonding ioctl (e.g. SIOCBONDENSLAVE, SIOCBONDRELEASE, etc.) with a non-existent slave interface name. This is reachable from userspace via the bonding ioctl interface with CAP_NET_ADMIN capability, making it a potential local denial-of-service vector. Fix by moving the slave_dbg() call after the NULL check. Fixes: e2a7420df2e0 ("bonding/main: convert to using slave printk macros") Cc: stable@vger.kernel.org # v5.2+ Signed-off-by: ZhaoJinming Link: https://patch.msgid.link/20260601085649.4029067-1-zhaojinming@uniontech.com Signed-off-by: Paolo Abeni Signed-off-by: Greg Kroah-Hartman

bonding: refuse to enslave CAN devices

2026-06-09T10:28:29+00:00

[ Upstream commit 8ba68464e4787b6a7ec938826e16124df20fd23d ] syzbot reported a kernel paging request crash in can_rx_unregister() inside net/can/af_can.c. The crash occurs because a virtual CAN device (vxcan) is being enslaved to a bonding master. During the enslavement process, the bonding driver mutates and modifies the network device states to fit an Ethernet-like aggregation model. However, CAN devices operate on a completely different Layer 2 architecture, relying on the CAN mid-layer private data structure (can_ml_priv) instead of standard Ethernet structures. Since bonding does not initialize or maintain these CAN structures, subsequent operations on the half-enslaved interface (such as closing associated sockets via isotp_release) lead to a null-pointer dereference when accessing the CAN receiver lists. Bonding CAN interfaces is architecturally invalid as CAN lacks MAC addresses, ARP capabilities, and standard Ethernet link-layer mechanisms. While generic loopback devices are blocked globally in net/core/dev.c, virtual CAN devices bypass this check because they do not carry the IFF_LOOPBACK flag, despite acting as local software-loopbacks. Fix this by explicitly blocking network devices of type ARPHRD_CAN from being enslaved at the very beginning of bond_enslave(). This prevents illegal state mutations, eliminates the resulting KASAN crashes, and avoids potential memory leaks from incomplete socket cleanups. As the CAN support has been added a long time after bonding the Fixes-tag points to the introduction of ARPHRD_CAN that would have needed a specific handling in bonding_main.c. Fixes: cd05acfe65ed ("[CAN]: Allocate protocol numbers for PF_CAN") Reported-by: syzbot+8ed98cbd0161632bce95@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=8ed98cbd0161632bce95 Signed-off-by: Oliver Hartkopp Acked-by: Jay Vosburgh Link: https://patch.msgid.link/20260526-bonding-candev-v1-1-ba1df400918a@hartkopp.net Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bonding: 3ad: implement proper RCU rules for port->aggregator

2026-05-23T11:07:13+00:00

[ Upstream commit c4f050ce06c56cfb5993268af4a5cb66ed1cd04e ] syzbot found a data-race in bond_3ad_get_active_agg_info / bond_3ad_state_machine_handler [1] which hints at lack of proper RCU implementation. Add __rcu qualifier to port->aggregator, and add proper RCU API. [1] BUG: KCSAN: data-race in bond_3ad_get_active_agg_info / bond_3ad_state_machine_handler write to 0xffff88813cf5c4b0 of 8 bytes by task 36 on cpu 0: ad_port_selection_logic drivers/net/bonding/bond_3ad.c:1659 [inline] bond_3ad_state_machine_handler+0x9d5/0x2d60 drivers/net/bonding/bond_3ad.c:2569 process_one_work kernel/workqueue.c:3302 [inline] process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3385 worker_thread+0x58a/0x780 kernel/workqueue.c:3466 kthread+0x22a/0x280 kernel/kthread.c:436 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 read to 0xffff88813cf5c4b0 of 8 bytes by task 22063 on cpu 1: __bond_3ad_get_active_agg_info drivers/net/bonding/bond_3ad.c:2858 [inline] bond_3ad_get_active_agg_info+0x8c/0x230 drivers/net/bonding/bond_3ad.c:2881 bond_fill_info+0xe0f/0x10f0 drivers/net/bonding/bond_netlink.c:853 rtnl_link_info_fill net/core/rtnetlink.c:906 [inline] rtnl_link_fill+0x1d7/0x4e0 net/core/rtnetlink.c:927 rtnl_fill_ifinfo+0xf8e/0x1380 net/core/rtnetlink.c:2168 rtmsg_ifinfo_build_skb+0x11c/0x1b0 net/core/rtnetlink.c:4453 rtmsg_ifinfo_event net/core/rtnetlink.c:4486 [inline] rtmsg_ifinfo+0x6d/0x110 net/core/rtnetlink.c:4495 __dev_notify_flags+0x76/0x390 net/core/dev.c:9790 netif_change_flags+0xac/0xd0 net/core/dev.c:9823 do_setlink+0x905/0x2950 net/core/rtnetlink.c:3180 rtnl_group_changelink net/core/rtnetlink.c:3813 [inline] __rtnl_newlink net/core/rtnetlink.c:3981 [inline] rtnl_newlink+0xf55/0x1400 net/core/rtnetlink.c:4109 rtnetlink_rcv_msg+0x64b/0x720 net/core/rtnetlink.c:6995 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2550 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:7022 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x5a8/0x680 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x5c8/0x6f0 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:787 [inline] __sock_sendmsg net/socket.c:802 [inline] ____sys_sendmsg+0x563/0x5b0 net/socket.c:2698 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2752 __sys_sendmsg net/socket.c:2784 [inline] __do_sys_sendmsg net/socket.c:2789 [inline] __se_sys_sendmsg net/socket.c:2787 [inline] __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2787 x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x0000000000000000 -> 0xffff88813cf5c400 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 22063 Comm: syz.0.31122 Tainted: G W syzkaller #0 PREEMPT(full) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Fixes: 47e91f56008b ("bonding: use RCU protection for 3ad xmit path") Reported-by: syzbot+9bb2ff2a4ab9e17307e1@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/69f0a82f.050a0220.3aadc4.0000.GAE@google.com/ Signed-off-by: Eric Dumazet Cc: Jay Vosburgh Cc: Andrew Lunn Link: https://patch.msgid.link/20260428123207.3809211-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bonding: print churn state via netlink

2026-05-23T11:07:12+00:00

[ Upstream commit 4916f2e2f3fc9aef289fcd07949301e5c29094c2 ] Currently, the churn state is printed only in sysfs. Add netlink support so users could get the state via netlink. Signed-off-by: Hangbin Liu Link: https://patch.msgid.link/20260224020215.6012-1-liuhangbin@gmail.com Signed-off-by: Paolo Abeni Stable-dep-of: c4f050ce06c5 ("bonding: 3ad: implement proper RCU rules for port->aggregator") Signed-off-by: Sasha Levin

net: bonding: fix use-after-free in bond_xmit_broadcast()

2026-04-11T12:26:23+00:00

[ Upstream commit 2884bf72fb8f03409e423397319205de48adca16 ] bond_xmit_broadcast() reuses the original skb for the last slave (determined by bond_is_last_slave()) and clones it for others. Concurrent slave enslave/release can mutate the slave list during RCU-protected iteration, changing which slave is "last" mid-loop. This causes the original skb to be double-consumed (double-freed). Replace the racy bond_is_last_slave() check with a simple index comparison (i + 1 == slaves_count) against the pre-snapshot slave count taken via READ_ONCE() before the loop. This preserves the zero-copy optimization for the last slave while making the "last" determination stable against concurrent list mutations. The UAF can trigger the following crash: ================================================================== BUG: KASAN: slab-use-after-free in skb_clone Read of size 8 at addr ffff888100ef8d40 by task exploit/147 CPU: 1 UID: 0 PID: 147 Comm: exploit Not tainted 7.0.0-rc3+ #4 PREEMPTLAZY Call Trace: dump_stack_lvl (lib/dump_stack.c:123) print_report (mm/kasan/report.c:379 mm/kasan/report.c:482) kasan_report (mm/kasan/report.c:597) skb_clone (include/linux/skbuff.h:1724 include/linux/skbuff.h:1792 include/linux/skbuff.h:3396 net/core/skbuff.c:2108) bond_xmit_broadcast (drivers/net/bonding/bond_main.c:5334) bond_start_xmit (drivers/net/bonding/bond_main.c:5567 drivers/net/bonding/bond_main.c:5593) dev_hard_start_xmit (include/linux/netdevice.h:5325 include/linux/netdevice.h:5334 net/core/dev.c:3871 net/core/dev.c:3887) __dev_queue_xmit (include/linux/netdevice.h:3601 net/core/dev.c:4838) ip6_finish_output2 (include/net/neighbour.h:540 include/net/neighbour.h:554 net/ipv6/ip6_output.c:136) ip6_finish_output (net/ipv6/ip6_output.c:208 net/ipv6/ip6_output.c:219) ip6_output (net/ipv6/ip6_output.c:250) ip6_send_skb (net/ipv6/ip6_output.c:1985) udp_v6_send_skb (net/ipv6/udp.c:1442) udpv6_sendmsg (net/ipv6/udp.c:1733) __sys_sendto (net/socket.c:730 net/socket.c:742 net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Allocated by task 147: Freed by task 147: The buggy address belongs to the object at ffff888100ef8c80 which belongs to the cache skbuff_head_cache of size 224 The buggy address is located 192 bytes inside of freed 224-byte region [ffff888100ef8c80, ffff888100ef8d60) Memory state around the buggy address: ffff888100ef8c00: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc ffff888100ef8c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888100ef8d00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ^ ffff888100ef8d80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb ffff888100ef8e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Fixes: 4e5bd03ae346 ("net: bonding: fix bond_xmit_broadcast return value error bug") Reported-by: Weiming Shi Signed-off-by: Xiang Mei Link: https://patch.msgid.link/20260326075553.3960562-1-xmei5@asu.edu Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin

net: bonding: fix NULL deref in bond_debug_rlb_hash_show

2026-03-25T10:10:42+00:00

[ Upstream commit 605b52497bf89b3b154674deb135da98f916e390 ] rlb_clear_slave intentionally keeps RLB hash-table entries on the rx_hashtbl_used_head list with slave set to NULL when no replacement slave is available. However, bond_debug_rlb_hash_show visites client_info->slave without checking if it's NULL. Other used-list iterators in bond_alb.c already handle this NULL-slave state safely: - rlb_update_client returns early on !client_info->slave - rlb_req_update_slave_clients, rlb_clear_slave, and rlb_rebalance compare slave values before visiting - lb_req_update_subnet_clients continues if slave is NULL The following NULL deref crash can be trigger in bond_debug_rlb_hash_show: [ 1.289791] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 1.292058] RIP: 0010:bond_debug_rlb_hash_show (drivers/net/bonding/bond_debugfs.c:41) [ 1.293101] RSP: 0018:ffffc900004a7d00 EFLAGS: 00010286 [ 1.293333] RAX: 0000000000000000 RBX: ffff888102b48200 RCX: ffff888102b48204 [ 1.293631] RDX: ffff888102b48200 RSI: ffffffff839daad5 RDI: ffff888102815078 [ 1.293924] RBP: ffff888102815078 R08: ffff888102b4820e R09: 0000000000000000 [ 1.294267] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888100f929c0 [ 1.294564] R13: ffff888100f92a00 R14: 0000000000000001 R15: ffffc900004a7ed8 [ 1.294864] FS: 0000000001395380(0000) GS:ffff888196e75000(0000) knlGS:0000000000000000 [ 1.295239] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.295480] CR2: 0000000000000000 CR3: 0000000102adc004 CR4: 0000000000772ef0 [ 1.295897] Call Trace: [ 1.296134] seq_read_iter (fs/seq_file.c:231) [ 1.296341] seq_read (fs/seq_file.c:164) [ 1.296493] full_proxy_read (fs/debugfs/file.c:378 (discriminator 1)) [ 1.296658] vfs_read (fs/read_write.c:572) [ 1.296981] ksys_read (fs/read_write.c:717) [ 1.297132] do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1)) [ 1.297325] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) Add a NULL check and print "(none)" for entries with no assigned slave. Fixes: caafa84251b88 ("bonding: add the debugfs interface to see RLB hash table") Reported-by: Weiming Shi Signed-off-by: Xiang Mei Link: https://patch.msgid.link/20260317005034.1888794-1-xmei5@asu.edu Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

bonding: prevent potential infinite loop in bond_header_parse()

2026-03-25T10:10:41+00:00

[ Upstream commit b7405dcf7385445e10821777143f18c3ce20fa04 ] bond_header_parse() can loop if a stack of two bonding devices is setup, because skb->dev always points to the hierarchy top. Add new "const struct net_device *dev" parameter to (struct header_ops)->parse() method to make sure the recursion is bounded, and that the final leaf parse method is called. Fixes: 950803f72547 ("bonding: fix type confusion in bond_setup_by_slave()") Signed-off-by: Eric Dumazet Reviewed-by: Jiayuan Chen Tested-by: Jiayuan Chen Cc: Jay Vosburgh Cc: Andrew Lunn Link: https://patch.msgid.link/20260315104152.1436867-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin