Description
In the Linux kernel, the following vulnerability has been resolved: veth: fix skb length accounting after XDP frag adjustment veth exposes non-linear skb fragments through an xdp_buff. If an XDP program adjusts the fragment area, veth_xdp_rcv_skb() copies xdp_frags_size back to skb->data_len but leaves skb->len containing the old fragment contribution. After a fragment shrink, this makes skb_headlen() larger than the actual linear area. In the reproduced UDP receive path, __skb_datagram_iter() copied 1024 bytes past the actual linear tail to userspace, starting at struct skb_shared_info. The copied bytes included the affected skb's nr_frags, xdp_frags_size, and a kernel pointer from skb_shinfo(skb)->frags[0]. Real packet data was displaced by the same amount and truncated at the end. Subtract the old data_len before replacing it and add the new data_len afterwards, keeping skb->len and skb->data_len synchronized. Additionally, bpf_xdp_pull_data() can advance data_end while leaving frags present. The skb is then still non-linear, so the old __skb_put(skb, off) triggers SKB_LINEAR_ASSERT(). Use skb_set_tail_pointer() and update skb->len explicitly instead, following bpf_prog_run_generic_xdp(). Unlike __skb_put(), skb_set_tail_pointer() does not require a linear skb. A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by 1024 bytes from its fragment area. Before the fix, all 10 runs produced corrupted payloads. After the fix, all 10 runs matched the expected payload exactly. A forced-tailroom reproducer also exercises bpf_xdp_pull_data() with frags still present; the old code triggers SKB_LINEAR_ASSERT(), while this fix passes 10/10 runs.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
718a18a0c8a67f97781e40bdef7cdd055c430996 to < 0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5affected718a18a0c8a67f97781e40bdef7cdd055c430996 to < 2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139affected718a18a0c8a67f97781e40bdef7cdd055c430996 to < 41b96667d42b74bb4b137f1bb78b611a953c5943affected718a18a0c8a67f97781e40bdef7cdd055c430996 to < cdf745b7a777f87f51666e5d8f4c6fc279bcf54daffected718a18a0c8a67f97781e40bdef7cdd055c430996 to < 3205b0652a37255dbb7ca8f3d942c8d8aa677c21affected718a18a0c8a67f97781e40bdef7cdd055c430996 to < cb6379feaaff11c4e1e79c26c745ffa23182768aaffected
Linux Linux
Default version status: affected
5.18affected0 to < 5.18unaffected6.1.184 to ≤ 6.1.*unaffected6.6.152 to ≤ 6.6.*unaffected6.12.104 to ≤ 6.12.*unaffected6.18.45 to ≤ 6.18.*unaffected7.1.9 to ≤ 7.1.*unaffected7.2 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/0c3024afabb8064b141f3cedcb1ddd6ab05ad9d5 ↗
- https://git.kernel.org/stable/c/2f2a7f3f8b9f1bffc9b0488aa02b6951b2aec139 ↗
- https://git.kernel.org/stable/c/41b96667d42b74bb4b137f1bb78b611a953c5943 ↗
- https://git.kernel.org/stable/c/cdf745b7a777f87f51666e5d8f4c6fc279bcf54d ↗
- https://git.kernel.org/stable/c/3205b0652a37255dbb7ca8f3d942c8d8aa677c21 ↗
- https://git.kernel.org/stable/c/cb6379feaaff11c4e1e79c26c745ffa23182768a ↗