CVE-2025-68245
Description
In the Linux kernel, the following vulnerability has been resolved:
net: netpoll: fix incorrect refcount handling causing incorrect cleanup
commit efa95b01da18 ("netpoll: fix use after free") incorrectly ignored the refcount and prematurely set dev->npinfo to NULL during netpoll cleanup, leading to improper behavior and memory leaks.
Scenario causing lack of proper cleanup:
1) A netpoll is associated with a NIC (e.g., eth0) and netdev->npinfo is allocated, and refcnt = 1 - Keep in mind that npinfo is shared among all netpoll instances. In this case, there is just one.
2) Another netpoll is also associated with the same NIC and npinfo->refcnt += 1. - Now dev->npinfo->refcnt = 2; - There is just one npinfo associated to the netdev.
3) When the first netpolls goes to clean up: - The first cleanup succeeds and clears np->dev->npinfo, ignoring refcnt. - It basically calls RCU_INIT_POINTER(np->dev->npinfo, NULL); - Set dev->npinfo = NULL, without proper cleanup - No ->ndo_netpoll_cleanup() is either called
4) Now the second target tries to clean up - The second cleanup fails because np->dev->npinfo is already NULL. * In this case, ops->ndo_netpoll_cleanup() was never called, and the skb pool is not cleaned as well (for the second netpoll instance) - This leaks npinfo and skbpool skbs, which is clearly reported by kmemleak.
Revert commit efa95b01da18 ("netpoll: fix use after free") and adds clarifying comments emphasizing that npinfo cleanup should only happen once the refcount reaches zero, ensuring stable and correct netpoll behavior.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
In the Linux kernel, a netpoll refcount handling bug causes memory leaks and improper cleanup when multiple netpoll instances share a NIC.
Vulnerability
The vulnerability stems from incorrect refcount handling in the Linux kernel's netpoll cleanup code. A previous fix (commit efa95b01da18) attempted to address a use-after-free issue but prematurely set dev->npinfo to NULL without considering the reference count, leading to improper cleanup and memory leaks.
Exploitation
Exploitation occurs when multiple netpoll instances are associated with the same network interface. The shared npinfo structure has a reference count incremented per instance. When one instance is cleaned up, it sets dev->npinfo to NULL regardless of remaining references, causing subsequent instances to fail cleanup, as they see a NULL pointer and skip necessary operations like ndo_netpoll_cleanup() and skb pool deallocation.
Impact
An attacker able to trigger this scenario (e.g., through netpoll usage) can cause memory leaks of npinfo structures and associated skb pools, as reported by kmemleak. This can lead to resource exhaustion over time, degrading system performance and stability.
Mitigation
The fix reverts the faulty commit efa95b01da18 and adds clarifying comments ensuring refcount is respected. The corrected behavior is included in stable kernel updates [1][2][3][4].
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
1Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
8- git.kernel.org/stable/c/49c8d2c1f94cc2f4d1a108530d7ba52614b874c2nvd
- git.kernel.org/stable/c/4afd4ebbad52aa146838ec23082ba393e426a2bbnvd
- git.kernel.org/stable/c/890472d6fbf062e6de7fdd56642cb305ab79d669nvd
- git.kernel.org/stable/c/8e6a50edad11e3e1426e4c29e7aa6201f3468ac2nvd
- git.kernel.org/stable/c/9a51b5ccd1c79afec1c03a4e1e6688da52597556nvd
- git.kernel.org/stable/c/9b0bb18b4b9dc017c1825a2c5e763615e34a1593nvd
- git.kernel.org/stable/c/c645693180a98606c430825223d2029315d85e9dnvd
- git.kernel.org/stable/c/c79a6d9da29219616b118a3adce9a14cd30f9bd0nvd
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