Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  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.