ipv6: account for fraggap on the paged allocation path

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Summary

CVECVE-2026-53362
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-04 12:17:02 UTC
Updated2026-07-04 12:17:02 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ipv6: account for fraggap on the paged allocation path In __ip6_append_data(), when the paged-allocation branch is taken (MSG_MORE / NETIF_F_SG / large fraglen), alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap (datalen = length + fraggap). When fraggap is non-zero, this is not the first skb and transhdrlen is zero. The fraggap bytes carried over from the previous skb are copied just past the fragment headers in the new skb's linear area. The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount, and the copy writes past skb->end into the trailing skb_shared_info. An unprivileged user can trigger this via a UDPv6 socket using MSG_MORE together with MSG_SPLICE_PAGES. The bad accounting was introduced by commit 773ba4fe9104 ("ipv6: avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix __ip6_append_data()'s handling of MSG_SPLICE_PAGES"), the negative copy value caused -EINVAL to be returned. That later commit allowed MSG_SPLICE_PAGES to proceed in this case, making the corruption triggerable. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic. Since a negative copy is no longer expected for a valid MSG_SPLICE_PAGES case, remove the MSG_SPLICE_PAGES exception from the negative copy check.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 773ba4fe9104a64a54d1c00f0fb6ffb95def2b03 14200d435af9a9eeb444f529fc2f689a236b7962 git Not specified
CNA Linux Linux affected 773ba4fe9104a64a54d1c00f0fb6ffb95def2b03 65fb14cbebb0cd0eff903a22d33537ddc8b95769 git Not specified
CNA Linux Linux affected 773ba4fe9104a64a54d1c00f0fb6ffb95def2b03 46f201f8b4c39633a1fa3dc12459f506d470993d git Not specified
CNA Linux Linux affected 773ba4fe9104a64a54d1c00f0fb6ffb95def2b03 6374fb9edf72c67a118a2c214a0dddd04c921e0a git Not specified
CNA Linux Linux affected 773ba4fe9104a64a54d1c00f0fb6ffb95def2b03 e9eacf19281ea2498b36291b56c9606118c2d74e git Not specified
CNA Linux Linux affected 773ba4fe9104a64a54d1c00f0fb6ffb95def2b03 736b380e28d0480c7bc3e022f1950f31fe53a7c5 git Not specified
CNA Linux Linux affected 6.0 Not specified
CNA Linux Linux unaffected 6.0 semver Not specified
CNA Linux Linux unaffected 6.1.177 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.144 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.95 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.38 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.3 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/e9eacf19281ea2498b36291b56c9606118c2d74e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/736b380e28d0480c7bc3e022f1950f31fe53a7c5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/14200d435af9a9eeb444f529fc2f689a236b7962 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/46f201f8b4c39633a1fa3dc12459f506d470993d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/65fb14cbebb0cd0eff903a22d33537ddc8b95769 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6374fb9edf72c67a118a2c214a0dddd04c921e0a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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