CVE-2026-80841net/packet: defer vmalloc TX_RING free until skbs finish

Official description

In the Linux kernel, the following vulnerability has been resolved: net/packet: defer vmalloc TX_RING free until skbs finish AF_PACKET TX_RING skbs keep a raw pointer to their ring frame. The skb page references preserve page-backed ring blocks after pg_vec is freed, but they do not preserve a vmalloc mapping. tpacket_destruct_skb() currently drops the pending reference before writing the timestamp and TP_STATUS_AVAILABLE to the frame. Move the decrement after those stores. The smp_wmb() in __packet_set_status() orders the frame stores before the decrement. Also recheck pending TX frames under pg_vec_lock before non-closing ring replacement, so a racing send cannot add a pending skb between the initial check and the ring swap. Ring allocation can produce a mixture of page-backed and vmalloc-backed blocks. Allocate deferred-work storage during TX ring setup when the first vmalloc-backed block is encountered, and keep its pointer in the pg_vec allocation header. If allocation fails, return -ENOMEM from ring setup. On socket close, a non-NULL pointer identifies a vmalloc-backed vector without a scan. If TX skbs remain, defer the whole vector to system_long_wq. After pg_vec is detached, a late destructor can skip the pending decrement. Use socket write-memory accounting as the deferred lifetime gate instead: an skb remains charged through its final sock_wfree(), after all ring-frame accesses. The delayed work retains a socket reference and reschedules itself until no TX skbs remain. Move pending_refcnt release to packet_sock_destruct() so late skb destructors and deferred cleanup can safely use it after packet_release(). Page-backed teardown remains synchronous, and no lock is added to the TX completion hot path.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ed126ca71d4d949ad99f40b974a8f7685e808f8b
• https://git.kernel.org/stable/c/debf9f50140b3df3949ebcb97d4450f8993fe32d
• https://git.kernel.org/stable/c/4ce6e2d2e38055b2012bd5fdb0c8a8183c8a1b0c
• https://git.kernel.org/stable/c/ed25ed29034ddc3dbe451ccbaa58ab9932f99d8b
• https://git.kernel.org/stable/c/0189dce07db2dc059ae0570e06758ec4233c6e11
• https://git.kernel.org/stable/c/550d00aa58193fb649a09a9c9e338c685adad784
• https://git.kernel.org/stable/c/992cc9f94ca924089a506ba9b327caa9af797529