xsk: fix buffer leak in xsk_drop_skb() for AF_XDP multi-buffer Tx

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74560
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 13:18:01 UTC
Updated2026-08-15 13:18:01 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: xsk: fix buffer leak in xsk_drop_skb() for AF_XDP multi-buffer Tx This patch is inspired by the check[1] from sashiko. It says when overflow happens, the address of cq to be published is invalid. Actually the severer thing is the whole process of publishing the address of cq in this particular case is not right: it should truely publish the address and advance the cached_prod in cq as long as it reads descriptors from txq. The following is the full analysis. xsk_drop_skb() is called in three places, which all discard a partially built multi-buffer skb: 1) xsk_build_skb() -EOVERFLOW error path: packet exceeds MAX_SKB_FRAGS 2) __xsk_generic_xmit() post-loop cleanup: an invalid descriptor in the TX ring prevents the partial packet from completing 3) xsk_release(): socket close while xs->skb holds an incomplete packet In all three cases, the TX descriptors for the already-processed frags have been consumed from the TX ring (xskq_cons_release), and CQ slots have been reserved. However, xsk_drop_skb() calls xsk_consume_skb() which cancels the CQ reservations via xsk_cq_cancel_locked(). Since the buffer addresses never appear in the completion queue, userspace permanently loses track of these buffers. Fix this by letting consume_skb() trigger the existing xsk_destruct_skb destructor, which already submits buffer addresses to the CQ via xsk_cq_submit_addr_locked(). Note that cancelling the descriptors back to the TX ring (via xskq_cons_cancel_n) is not a appropriate option because an oversized packet that always exceeds MAX_SKB_FRAGS would be retried indefinitely, which is an obviously deadlock bug in the TX path. Also move the desc->addr assignment in xsk_build_skb() above the overflow check so that the current descriptor's address is recorded before a potential -EOVERFLOW jump to free_err, consistent with the zerocopy path in xsk_build_skb_zerocopy(). [1]: https://lore.kernel.org/all/[email protected]/

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected cf24f5a5feeaae34c1a34d1e04f8ac697290427a 05e283466b86e0b25a5209a3eafe87aa9886064a git Not specified
CNA Linux Linux affected cf24f5a5feeaae34c1a34d1e04f8ac697290427a a0528ab6af62bf57153caaf8ea28e5fcb0e18fd4 git Not specified
CNA Linux Linux affected cf24f5a5feeaae34c1a34d1e04f8ac697290427a a3c8382ebce4780c6b3ace2c09bc342313ac0186 git Not specified
CNA Linux Linux affected 6.6 Not specified
CNA Linux Linux unaffected 6.6 semver Not specified
CNA Linux Linux unaffected 6.18.44 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc6 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a0528ab6af62bf57153caaf8ea28e5fcb0e18fd4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/05e283466b86e0b25a5209a3eafe87aa9886064a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a3c8382ebce4780c6b3ace2c09bc342313ac0186 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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