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CVE-2025-68169 json

netpoll: Fix deadlock in memory allocation under spinlock

published 2025-12-16 10 mo ago modified 2026-10-14 26 d ago also EUVD-2025-203727

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 8%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

netpoll: Fix deadlock in memory allocation under spinlock

Fix a AA deadlock in refill_skbs() where memory allocation while holding skb_pool->lock can trigger a recursive lock acquisition attempt.

The deadlock scenario occurs when the system is under severe memory pressure:

1. refill_skbs() acquires skb_pool->lock (spinlock) 2. alloc_skb() is called while holding the lock 3. Memory allocator fails and calls slab_out_of_memory() 4. This triggers printk() for the OOM warning 5. The console output path calls netpoll_send_udp() 6. netpoll_send_udp() attempts to acquire the same skb_pool->lock 7. Deadlock: the lock is already held by the same CPU

Call stack: refill_skbs() spin_lock_irqsave(&skb_pool->lock) <- lock acquired __alloc_skb() kmem_cache_alloc_node_noprof() slab_out_of_memory() printk() console_flush_all() netpoll_send_udp() skb_dequeue() spin_lock_irqsave(&skb_pool->lock) <- deadlock attempt

This bug was exposed by commit 248f6571fd4c51 ("netpoll: Optimize skb refilling on critical path") which removed refill_skbs() from the critical path (where nested printk was being deferred), letting nested printk being called from inside refill_skbs()

Refactor refill_skbs() to never allocate memory while holding the spinlock.

Another possible solution to fix this problem is protecting the refill_skbs() from nested printks, basically calling printk_deferred_{enter,exit}() in refill_skbs(), then, any nested pr_warn() would be deferred.

I prefer this approach, given I _think_ it might be a good idea to move the alloc_skb() from GFP_ATOMIC to GFP_KERNEL in the future, so, having the alloc_skb() outside of the lock will be necessary step.

There is a possible TOCTOU issue when checking for the pool length, and queueing the new allocated skb, but, this is not an issue, given that an extra SKB in the pool is harmless and it will be eventually used.

Patch / fix

  • Linux Linux 6.17.8, 6.18
  • linux Debian 14 6.17.8-1

debian advisories DEBIAN-CVE-2025-68169

  • linux Ubuntu 25.10 6.17.0-14.14
  • linux-aws Ubuntu 25.10 6.17.0-1007.7
  • linux-gcp Ubuntu 25.10 6.17.0-1007.7
  • linux-azure Ubuntu 25.10 6.17.0-1008.8
  • linux-raspi Ubuntu 25.10 6.17.0-1008.8
  • linux-riscv Ubuntu 25.10 6.17.0-14.14.1
  • linux-oracle Ubuntu 25.10 6.17.0-1007.7
  • linux-aws-6.17 Ubuntu 24.04 LTS 6.17.0-1007.7~24.04.1

ubuntu advisories UBUNTU-CVE-2025-68169

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-68169 updated cvss 5.5

kernel: Linux kernel: Denial of Service via deadlock in netpoll memory allocation

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.19% chance of exploitation in the next 30 days, higher than 8% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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