From 479d589b40b836442bbdadc3fdb37f001bb67f26 Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Thu, 26 Feb 2026 16:03:01 +0800 Subject: [PATCH] bpf/bonding: reject vlan+srcmac xmit_hash_policy change when XDP is loaded bond_option_mode_set() already rejects mode changes that would make a loaded XDP program incompatible via bond_xdp_check(). However, bond_option_xmit_hash_policy_set() has no such guard. For 802.3ad and balance-xor modes, bond_xdp_check() returns false when xmit_hash_policy is vlan+srcmac, because the 802.1q payload is usually absent due to hardware offload. This means a user can: 1. Attach a native XDP program to a bond in 802.3ad/balance-xor mode with a compatible xmit_hash_policy (e.g. layer2+3). 2. Change xmit_hash_policy to vlan+srcmac while XDP remains loaded. This leaves bond->xdp_prog set but bond_xdp_check() now returning false for the same device. When the bond is later destroyed, dev_xdp_uninstall() calls bond_xdp_set(dev, NULL, NULL) to remove the program, which hits the bond_xdp_check() guard and returns -EOPNOTSUPP, triggering: WARN_ON(dev_xdp_install(dev, mode, bpf_op, NULL, 0, NULL)) Fix this by rejecting xmit_hash_policy changes to vlan+srcmac when an XDP program is loaded on a bond in 802.3ad or balance-xor mode. commit 39a0876d595b ("net, bonding: Disallow vlan+srcmac with XDP") introduced bond_xdp_check() which returns false for 802.3ad/balance-xor modes when xmit_hash_policy is vlan+srcmac. The check was wired into bond_xdp_set() to reject XDP attachment with an incompatible policy, but the symmetric path -- preventing xmit_hash_policy from being changed to an incompatible value after XDP is already loaded -- was left unguarded in bond_option_xmit_hash_policy_set(). Note: commit 094ee6017ea0 ("bonding: check xdp prog when set bond mode") later added a similar guard to bond_option_mode_set(), but bond_option_xmit_hash_policy_set() remained unprotected. Reported-by: syzbot+5a287bcdc08104bc3132@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/6995aff6.050a0220.2eeac1.014e.GAE@google.com/T/ Fixes: 39a0876d595b ("net, bonding: Disallow vlan+srcmac with XDP") Signed-off-by: Jiayuan Chen Link: https://patch.msgid.link/20260226080306.98766-2-jiayuan.chen@linux.dev Signed-off-by: Paolo Abeni --- drivers/net/bonding/bond_main.c | 9 +++++++-- drivers/net/bonding/bond_options.c | 2 ++ include/net/bonding.h | 1 + 3 files changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index a1de08ee3815..14ed91391fcc 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -324,7 +324,7 @@ static bool bond_sk_check(struct bonding *bond) } } -bool bond_xdp_check(struct bonding *bond, int mode) +bool __bond_xdp_check(int mode, int xmit_policy) { switch (mode) { case BOND_MODE_ROUNDROBIN: @@ -335,7 +335,7 @@ bool bond_xdp_check(struct bonding *bond, int mode) /* vlan+srcmac is not supported with XDP as in most cases the 802.1q * payload is not in the packet due to hardware offload. */ - if (bond->params.xmit_policy != BOND_XMIT_POLICY_VLAN_SRCMAC) + if (xmit_policy != BOND_XMIT_POLICY_VLAN_SRCMAC) return true; fallthrough; default: @@ -343,6 +343,11 @@ bool bond_xdp_check(struct bonding *bond, int mode) } } +bool bond_xdp_check(struct bonding *bond, int mode) +{ + return __bond_xdp_check(mode, bond->params.xmit_policy); +} + /*---------------------------------- VLAN -----------------------------------*/ /* In the following 2 functions, bond_vlan_rx_add_vid and bond_vlan_rx_kill_vid, diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c index dcee384c2f06..7380cc4ee75a 100644 --- a/drivers/net/bonding/bond_options.c +++ b/drivers/net/bonding/bond_options.c @@ -1575,6 +1575,8 @@ static int bond_option_fail_over_mac_set(struct bonding *bond, static int bond_option_xmit_hash_policy_set(struct bonding *bond, const struct bond_opt_value *newval) { + if (bond->xdp_prog && !__bond_xdp_check(BOND_MODE(bond), newval->value)) + return -EOPNOTSUPP; netdev_dbg(bond->dev, "Setting xmit hash policy to %s (%llu)\n", newval->string, newval->value); bond->params.xmit_policy = newval->value; diff --git a/include/net/bonding.h b/include/net/bonding.h index 4ad5521e7731..395c6e281c5f 100644 --- a/include/net/bonding.h +++ b/include/net/bonding.h @@ -699,6 +699,7 @@ void bond_debug_register(struct bonding *bond); void bond_debug_unregister(struct bonding *bond); void bond_debug_reregister(struct bonding *bond); const char *bond_mode_name(int mode); +bool __bond_xdp_check(int mode, int xmit_policy); bool bond_xdp_check(struct bonding *bond, int mode); void bond_setup(struct net_device *bond_dev); unsigned int bond_get_num_tx_queues(void);