CVE-2026-31691

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: igb: remove napi_synchronize() in igb_down() When an AF_XDP zero-copy application terminates abruptly (e.g., kill -9), the XSK buffer pool is destroyed but NAPI polling continues. igb_clean_rx_irq_zc() repeatedly returns the full budget, preventing napi_complete_done() from clearing NAPI_STATE_SCHED. igb_down() calls napi_synchronize() before napi_disable() for each queue vector. napi_synchronize() spins waiting for NAPI_STATE_SCHED to clear, which never happens. igb_down() blocks indefinitely, the TX watchdog fires, and the TX queue remains permanently stalled. napi_disable() already handles this correctly: it sets NAPI_STATE_DISABLE. After a full-budget poll, __napi_poll() checks napi_disable_pending(). If set, it forces completion and clears NAPI_STATE_SCHED, breaking the loop that napi_synchronize() cannot. napi_synchronize() was added in commit 41f149a285da ("igb: Fix possible panic caused by Rx traffic arrival while interface is down"). napi_disable() provides stronger guarantees: it prevents further scheduling and waits for any active poll to exit. Other Intel drivers (ixgbe, ice, i40e) use napi_disable() without a preceding napi_synchronize() in their down paths. Remove redundant napi_synchronize() call and reorder napi_disable() before igb_set_queue_napi() so the queue-to-NAPI mapping is only cleared after polling has fully stopped.

Severity

MEDIUM

CVSS score

5.5 (v3.1)

Vulnerability status

Analyzed

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2026-04-27 18:16:54.610000

Last modified

2026-11-06 16:18:08.113000

View original CVE JSON

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  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-04-27T18:16:54.610",
  "lastModified": "2026-11-06T16:18:08.113",
  "vulnStatus": "Analyzed",
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nigb: remove napi_synchronize() in igb_down()\n\nWhen an AF_XDP zero-copy application terminates abruptly (e.g., kill -9),\nthe XSK buffer pool is destroyed but NAPI polling continues.\nigb_clean_rx_irq_zc() repeatedly returns the full budget, preventing\nnapi_complete_done() from clearing NAPI_STATE_SCHED.\n\nigb_down() calls napi_synchronize() before napi_disable() for each queue\nvector. napi_synchronize() spins waiting for NAPI_STATE_SCHED to clear,\nwhich never happens. igb_down() blocks indefinitely, the TX watchdog\nfires, and the TX queue remains permanently stalled.\n\nnapi_disable() already handles this correctly: it sets NAPI_STATE_DISABLE.\nAfter a full-budget poll, __napi_poll() checks napi_disable_pending(). If\nset, it forces completion and clears NAPI_STATE_SCHED, breaking the loop\nthat napi_synchronize() cannot.\n\nnapi_synchronize() was added in commit 41f149a285da (\"igb: Fix possible\npanic caused by Rx traffic arrival while interface is down\").\nnapi_disable() provides stronger guarantees: it prevents further\nscheduling and waits for any active poll to exit.\nOther Intel drivers (ixgbe, ice, i40e) use napi_disable() without a\npreceding napi_synchronize() in their down paths.\n\nRemove redundant napi_synchronize() call and reorder napi_disable()\nbefore igb_set_queue_napi() so the queue-to-NAPI mapping is only\ncleared after polling has fully stopped."
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          "userInteraction": "NONE",
          "scope": "UNCHANGED",
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