CVE-2025-39945
In the Linux kernel, the following vulnerability has been resolved: cnic: Fix use-after-free bugs in cnic_delete_task The original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(), which does not guarantee that the delayed work item…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.16%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: cnic: Fix use-after-free bugs in cnic_delete_task The original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(), which does not guarantee that the delayed work item 'delete_task' has fully completed if it was already running. Additionally, the delayed work item is cyclic, the flush_workqueue() in cnic_cm_stop_bnx2x_hw() only blocks and waits for work items that were already queued to the workqueue prior to its invocation. Any work items submitted after flush_workqueue() is called are not included in the set of tasks that the flush operation awaits. This means that after the cyclic work items have finished executing, a delayed work item may still exist in the workqueue. This leads to use-after-free scenarios where the cnic_dev is deallocated by cnic_free_dev(), while delete_task remains active and attempt to dereference cnic_dev in cnic_delete_task(). A typical race condition is illustrated below: CPU 0 (cleanup) | CPU 1 (delayed work callback) cnic_netdev_event() | cnic_stop_hw() | cnic_delete_task() cnic_cm_stop_bnx2x_hw() | ... cancel_delayed_work() | /* the queue_delayed_work() flush_workqueue() | executes after flush_workqueue()*/ | queue_delayed_work() cnic_free_dev(dev)//free | cnic_delete_task() //new instance | dev = cp->dev; //use Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the cyclic delayed work item is properly canceled and that any ongoing execution of the work item completes before the cnic_dev is deallocated. Furthermore, since cancel_delayed_work_sync() uses __flush_work(work, true) to synchronously wait for any currently executing instance of the work item to finish, the flush_workqueue() becomes redundant and should be removed. This bug was identified through static analysis. To reproduce the issue and validate the fix, I simulated the cnic PCI device in QEMU and introduced intentional delays — such as inserting calls to ssleep() within the cnic_delete_task() function — to increase the likelihood of triggering the bug.
- CVSS 3.1
- 7.8 HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.16% probability · 5th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-416
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/0405055930264ea8fd26f4131466fa7652e5e47dPatch
- https://git.kernel.org/stable/c/0627e1481676669cae2df0d85b5ff13e7d24c390Patch
- https://git.kernel.org/stable/c/6e33a7eed587062ca8161ad1f4584882a860d697Patch
- https://git.kernel.org/stable/c/7b6a5b0a6b392263c3767fc945b311ea04b34bbdPatch
- https://git.kernel.org/stable/c/8eeb2091e72d75df8ceaa2172638d61b4cf8929aPatch
- https://git.kernel.org/stable/c/cfa7d9b1e3a8604afc84e9e51d789c29574fb216Patch
- https://git.kernel.org/stable/c/e1fcd4a9c09feac0902a65615e866dbf22616125Patch
- https://git.kernel.org/stable/c/fde6e73189f40ebcf0633aed2b68e731c25f3aa3Patch
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.