CVE-2026-64545

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

net, bpf: check master for NULL in xdp_master_redirect()

xdp_master_redirect() dereferences the result of netdev_master_upper_dev_get_rcu() without a NULL check, but that helper returns NULL when the receiving device has no upper-master adjacency.

The reach guard only checks netif_is_bond_slave(). On bond slave release bond_upper_dev_unlink() drops the upper-master adjacency before clearing IFF_SLAVE, so an XDP_TX reaching xdp_master_redirect() in that window still passes netif_is_bond_slave() while master is already NULL, and faults on master->flags at offset 0xb0:

BUG: kernel NULL pointer dereference, address: 00000000000000b0 RIP: 0010:xdp_master_redirect (net/core/filter.c:4432) Call Trace: xdp_master_redirect (net/core/filter.c:4432) bpf_prog_run_generic_xdp (include/net/xdp.h:700) do_xdp_generic (net/core/dev.c:5608) __netif_receive_skb_one_core (net/core/dev.c:6204) process_backlog (net/core/dev.c:6319) __napi_poll (net/core/dev.c:7729) net_rx_action (net/core/dev.c:7792) handle_softirqs (kernel/softirq.c:622) __dev_queue_xmit (include/linux/bottom_half.h:33) packet_sendmsg (net/packet/af_packet.c:3082) __sys_sendto (net/socket.c:2252) Kernel panic - not syncing: Fatal exception in interrupt

The missing check dates back to the original code; commit 1921f91298d1 (net, bpf: fix null-ptr-deref in xdp_master_redirect() for down master) later added the master->flags read where the fault now lands but kept the unconditional deref. Check master for NULL before use; a NULL master is treated the same as one that is not up.

Affected Software

References

• https://git.kernel.org/stable/c/03b743586a2469744e96e9c1015096d07240935d
• https://git.kernel.org/stable/c/3876318ea54e83eb70982b8280a3c5e4e32269bf
• https://git.kernel.org/stable/c/4edbcacca09f92b85d3951b6add11894b20a84bc
• https://git.kernel.org/stable/c/89c103d702b25ceb2d097faf854deb47b53b17ff
• https://git.kernel.org/stable/c/c99ca049e910d61ddbd28cc2c47242f2bfbb4970
• https://git.kernel.org/stable/c/e2a56441233131fe18a76001de347ecda217e40c
• https://git.kernel.org/stable/c/e82d8cc4321c373dc46e741cd2dfdaa7921fddb7