net: skbuff: do not leave stale header offsets after pskb_carve()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98271
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-06 09:18:16 UTC
Updated2026-10-19 10:18:28 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net: skbuff: do not leave stale header offsets after pskb_carve() pskb_carve_inside_header() and pskb_carve_inside_nonlinear() remove the first bytes of a packet and reallocate skb->head. All the headers that were present before the operation are gone, but both functions call skb_headers_offset_update(skb, 0), which is a no-op : skb->mac_header, skb->network_header, skb->transport_header and skb->csum_start keep their old values and now describe bytes which are no longer there. Both helpers size the new head from the old skb_end_offset(), so the stale offsets still land inside the new allocation. They point past skb_tail_pointer() though, to bytes that were never initialized. pskb_carve_inside_nonlinear() is the worst case, because it leaves a zombie skb with an empty linear part (skb->data == skb_tail_pointer(skb), skb_headlen(skb) == 0), while skb_mac_header_was_set() is still true and skb->mac_header is way ahead of skb->data. The only user of pskb_extract() is rds_tcp_data_recv(), and the carved skb is queued on tinc->ti_skb_list. When the RDS incoming message is released, rds_tcp_inc_free() calls skb_queue_purge(), which frees the skbs with SKB_DROP_REASON_QUEUE_PURGE. This is visible from drop_monitor, which then tries to pull back to the (bogus) mac header : skbuff: __skb_pull(len=234) skb len=6968 data_len=6968 headroom=0 headlen=0 tailroom=0 end-tail=384 mac=(234,14) mac_len=14 net=(248,40) trans=288 shinfo(txflags=0 nr_frags=1 gso(size=1428 type=16 segs=5)) csum(0x100120 start=288 offset=16 ip_summed=3 complete_sw=0 valid=1 level=0) hash(0x7b446c6c sw=0 l4=1) proto=0x86dd pkttype=0 iif=60 kernel BUG at ./include/linux/skbuff.h:2847! Add skb_carve_reset_headers() to mark the mac and transport headers as not set, reset the network header, clear skb->mac_len, and drop a now meaningless CHECKSUM_PARTIAL (csum_start no longer describes anything). Invalidate the inner offsets as well. Unlike mac_header and transport_header they have no "unset" sentinel, so a leftover non-zero value still looks like a real header. Zero skb->inner_mac_header, skb->inner_network_header, skb->inner_transport_header, skb->inner_protocol and skb->encapsulation, so that all the header state is invalidated in one place. v2: fixed an inaccurate changelog. The stale offsets stay inside the new skb->head, which is never smaller than the old one, they simply point past skb_tail_pointer() to bytes that are gone. Thanks to Xuanqiang Luo for insisting on this. Also invalidate the inner header state, as suggested by the netdev AI review : https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260911114922.621937-1-edumazet%40google.com

Risk And Classification

EPSS: 0.001750000 probability, percentile 0.063820000 (date 2026-10-06)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 6fa01ccd883021105e9f8af7d04b9f156fa3494a 75e4a3e62531738c124c8555a626426fca29d392 git Not specified
CNA Linux Linux affected 6fa01ccd883021105e9f8af7d04b9f156fa3494a bff8a8e53a6d290bc2777bde36d3cb6317b8463d git Not specified
CNA Linux Linux affected 6fa01ccd883021105e9f8af7d04b9f156fa3494a 12929ed66a5166177ef5f06d3da81e4f99993e90 git Not specified
CNA Linux Linux affected 6fa01ccd883021105e9f8af7d04b9f156fa3494a a5117e1eccac6ee3bd4aed7cacf8ebcb6b3eb309 git Not specified
CNA Linux Linux affected 4.7 Not specified
CNA Linux Linux unaffected 4.7 semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.54 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.8 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a5117e1eccac6ee3bd4aed7cacf8ebcb6b3eb309 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/12929ed66a5166177ef5f06d3da81e4f99993e90 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/75e4a3e62531738c124c8555a626426fca29d392 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bff8a8e53a6d290bc2777bde36d3cb6317b8463d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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