In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
veth: fix skb length accounting after XDP frag adjustment<\/p>\n
veth exposes non-linear skb fragments through an xdp_buff. If an XDP
\nprogram adjusts the fragment area, veth_xdp_rcv_skb() copies
\nxdp_frags_size back to skb->data_len but leaves skb->len containing the
\nold fragment contribution.<\/p>\n
After a fragment shrink, this makes skb_headlen() larger than the actual
\nlinear area. In the reproduced UDP receive path, __skb_datagram_iter()
\ncopied 1024 bytes past the actual linear tail to userspace, starting at
\nstruct skb_shared_info. The copied bytes included the affected skb’s
\nnr_frags, xdp_frags_size, and a kernel pointer from
\nskb_shinfo(skb)->frags[0]. Real packet data was displaced by the same
\namount and truncated at the end.<\/p>\n
Subtract the old data_len before replacing it and add the new data_len
\nafterwards, keeping skb->len and skb->data_len synchronized.<\/p>\n
Additionally, bpf_xdp_pull_data() can advance data_end while leaving
\nfrags present. The skb is then still non-linear, so the old
\n__skb_put(skb, off) triggers SKB_LINEAR_ASSERT().<\/p>\n
Use skb_set_tail_pointer() and update skb->len explicitly instead,
\nfollowing bpf_prog_run_generic_xdp(). Unlike __skb_put(),
\nskb_set_tail_pointer() does not require a linear skb.<\/p>\n
A 60000-byte UDP datagram on a veth pair with MTU 64000 was shortened by
\n1024 bytes from its fragment area. Before the fix, all 10 runs produced
\ncorrupted payloads. After the fix, all 10 runs matched the expected
\npayload exactly. A forced-tailroom reproducer also exercises
\nbpf_xdp_pull_data() with frags still present; the old code triggers
\nSKB_LINEAR_ASSERT(), while this fix passes 10\/10 runs.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
veth: fix skb length accounting after XDP frag adjustment<\/p>\n
veth exposes non-linear skb fragments through an xdp_buff. If an XDP
\npro<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-11218","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/11218","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=11218"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=11218"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=11218"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}