Affected: Linux

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

bonding: provide a net pointer to __skb_flow_dissect()

After 3cbf4ffba5ee ("net: plumb network namespace into __skb_flow_dissect") we have to provide a net pointer to __skb_flow_dissect(), either via skb->dev, skb->sk, or a user provided pointer.

In the following case, syzbot was able to cook a bare skb.

WARNING: net/core/flow_dissector.c:1131 at __skb_flow_dissect+0xb57/0x68b0 net/core/flow_dissector.c:1131, CPU#1: syz.2.1418/11053 Call Trace: <TASK> bond_flow_dissect drivers/net/bonding/bond_main.c:4093 [inline] __bond_xmit_hash+0x2d7/0xba0 drivers/net/bonding/bond_main.c:4157 bond_xmit_hash_xdp drivers/net/bonding/bond_main.c:4208 [inline] bond_xdp_xmit_3ad_xor_slave_get drivers/net/bonding/bond_main.c:5139 [inline] bond_xdp_get_xmit_slave+0x1fd/0x710 drivers/net/bonding/bond_main.c:5515 xdp_master_redirect+0x13f/0x2c0 net/core/filter.c:4388 bpf_prog_run_xdp include/net/xdp.h:700 [inline] bpf_test_run+0x6b2/0x7d0 net/bpf/test_run.c:421 bpf_prog_test_run_xdp+0x795/0x10e0 net/bpf/test_run.c:1390 bpf_prog_test_run+0x2c7/0x340 kernel/bpf/syscall.c:4703 __sys_bpf+0x562/0x860 kernel/bpf/syscall.c:6182 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline] __se_sys_bpf kernel/bpf/syscall.c:6272 [inline] __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6272 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94