Entreprise française de cybersécurité depuis 2004
☎ 03 60 47 09 81 - info@securiteinfo.com
☎ 03 60 47 09 81 - info@securiteinfo.com
In the Linux kernel, the following vulnerability has been resolved:net: fix udp gso skb_segment after pull from frag_listCommit a1e40ac5b5e9 ("net: gso: fix udp gso fraglist segmentation afterpull from frag_list") detected invalid geometry in frag_list skbs andredirects them from skb_segment_list to more robust skb_segment. But somepackets with modified geometry can also hit bugs in that code. We don'tknow how many such cases exist. Addressing each one by one also requirestouching the complex skb_segment code, which risks introducing bugs forother types of skbs. Instead, linearize all these packets that fail thebasic invariants on gso fraglist skbs. That is more robust.If only part of the fraglist payload is pulled into head_skb, it willalways cause exception when splitting skbs by skb_segment. For detailedcall stack information, see below.Valid SKB_GSO_FRAGLIST skbs- consist of two or more segments- the head_skb holds the protocol headers plus first gso_size- one or more frag_list skbs hold exactly one segment- all but the last must be gso_sizeOptional datapath hooks such as NAT and BPF (bpf_skb_pull_data) canmodify fraglist skbs, breaking these invariants.In extreme cases they pull one part of data into skb linear. For UDP,this causes three payloads with lengths of (11,11,10) bytes werepulled tail to become (12,10,10) bytes.The skbs no longer meets the above SKB_GSO_FRAGLIST conditions becausepayload was pulled into head_skb, it needs to be linearized before passto regular skb_segment. skb_segment+0xcd0/0xd14 __udp_gso_segment+0x334/0x5f4 udp4_ufo_fragment+0x118/0x15c inet_gso_segment+0x164/0x338 skb_mac_gso_segment+0xc4/0x13c __skb_gso_segment+0xc4/0x124 validate_xmit_skb+0x9c/0x2c0 validate_xmit_skb_list+0x4c/0x80 sch_direct_xmit+0x70/0x404 __dev_queue_xmit+0x64c/0xe5c neigh_resolve_output+0x178/0x1c4 ip_finish_output2+0x37c/0x47c __ip_finish_output+0x194/0x240 ip_finish_output+0x20/0xf4 ip_output+0x100/0x1a0 NF_HOOK+0xc4/0x16c ip_forward+0x314/0x32c ip_rcv+0x90/0x118 __netif_receive_skb+0x74/0x124 process_backlog+0xe8/0x1a4 __napi_poll+0x5c/0x1f8 net_rx_action+0x154/0x314 handle_softirqs+0x154/0x4b8 [118.376811] [C201134] rxq0_pus: [name:bug&]kernel BUG at net/core/skbuff.c:4278! [118.376829] [C201134] rxq0_pus: [name:traps&]Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP [118.470774] [C201134] rxq0_pus: [name:mrdump&]Kernel Offset: 0x178cc00000 from 0xffffffc008000000 [118.470810] [C201134] rxq0_pus: [name:mrdump&]PHYS_OFFSET: 0x40000000 [118.470827] [C201134] rxq0_pus: [name:mrdump&]pstate: 60400005 (nZCv daif +PAN -UAO) [118.470848] [C201134] rxq0_pus: [name:mrdump&]pc : [0xffffffd79598aefc] skb_segment+0xcd0/0xd14 [118.470900] [C201134] rxq0_pus: [name:mrdump&]lr : [0xffffffd79598a5e8] skb_segment+0x3bc/0xd14 [118.470928] [C201134] rxq0_pus: [name:mrdump&]sp : ffffffc008013770
No PoCs from references.
- https://github.com/w4zu/Debian_security