CVE-2025-68245: net: netpoll: fix incorrect refcount handling causing incorrect cleanup
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 RCUINITPOINTER(np->dev->npinfo, NULL); - Set dev->npinfo = NULL, without proper cleanup - No ->ndonetpollcleanup() 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->ndonetpollcleanup() 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.
Affected Software
Remediation
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Revert commit efa95b01da18 ("netpoll: fix use after free") so npinfo cleanup occurs only when the refcount reaches zero.
Event History
Frequently Asked Questions
What is the severity of CVE-2025-68245?
CVE-2025-68245 has a severity rating that indicates a moderate risk due to incorrect reference count handling in the Linux kernel.
How do I fix CVE-2025-68245?
To fix CVE-2025-68245, update your Linux kernel to the latest stable version where this vulnerability has been resolved.
What are the potential impacts of CVE-2025-68245?
CVE-2025-68245 could lead to use-after-free vulnerabilities that may be exploited to crash the system or potentially allow unauthorized access.
Which versions of the Linux kernel are affected by CVE-2025-68245?
CVE-2025-68245 affects various versions of the Linux kernel prior to the fix implemented in commit efa95b01da18.
Is there a workaround for CVE-2025-68245?
Currently, the best mitigation for CVE-2025-68245 is to apply the recommended updates to the Linux kernel as no specific workarounds are described.