ghsa-g7c3-fwjq-9g8f
Vulnerability from github
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.
{
"affected": [],
"aliases": [
"CVE-2025-39945"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-04T08:15:47Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncnic: Fix use-after-free bugs in cnic_delete_task\n\nThe original code uses cancel_delayed_work() in cnic_cm_stop_bnx2x_hw(),\nwhich does not guarantee that the delayed work item \u0027delete_task\u0027 has\nfully completed if it was already running. Additionally, the delayed work\nitem is cyclic, the flush_workqueue() in cnic_cm_stop_bnx2x_hw() only\nblocks and waits for work items that were already queued to the\nworkqueue prior to its invocation. Any work items submitted after\nflush_workqueue() is called are not included in the set of tasks that the\nflush operation awaits. This means that after the cyclic work items have\nfinished executing, a delayed work item may still exist in the workqueue.\nThis leads to use-after-free scenarios where the cnic_dev is deallocated\nby cnic_free_dev(), while delete_task remains active and attempt to\ndereference cnic_dev in cnic_delete_task().\n\nA typical race condition is illustrated below:\n\nCPU 0 (cleanup) | CPU 1 (delayed work callback)\ncnic_netdev_event() |\n cnic_stop_hw() | cnic_delete_task()\n cnic_cm_stop_bnx2x_hw() | ...\n cancel_delayed_work() | /* the queue_delayed_work()\n flush_workqueue() | executes after flush_workqueue()*/\n | queue_delayed_work()\n cnic_free_dev(dev)//free | cnic_delete_task() //new instance\n | dev = cp-\u003edev; //use\n\nReplace cancel_delayed_work() with cancel_delayed_work_sync() to ensure\nthat the cyclic delayed work item is properly canceled and that any\nongoing execution of the work item completes before the cnic_dev is\ndeallocated. Furthermore, since cancel_delayed_work_sync() uses\n__flush_work(work, true) to synchronously wait for any currently\nexecuting instance of the work item to finish, the flush_workqueue()\nbecomes redundant and should be removed.\n\nThis bug was identified through static analysis. To reproduce the issue\nand validate the fix, I simulated the cnic PCI device in QEMU and\nintroduced intentional delays \u2014 such as inserting calls to ssleep()\nwithin the cnic_delete_task() function \u2014 to increase the likelihood\nof triggering the bug.",
"id": "GHSA-g7c3-fwjq-9g8f",
"modified": "2025-10-04T09:30:21Z",
"published": "2025-10-04T09:30:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39945"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0405055930264ea8fd26f4131466fa7652e5e47d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0627e1481676669cae2df0d85b5ff13e7d24c390"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6e33a7eed587062ca8161ad1f4584882a860d697"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7b6a5b0a6b392263c3767fc945b311ea04b34bbd"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8eeb2091e72d75df8ceaa2172638d61b4cf8929a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cfa7d9b1e3a8604afc84e9e51d789c29574fb216"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e1fcd4a9c09feac0902a65615e866dbf22616125"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fde6e73189f40ebcf0633aed2b68e731c25f3aa3"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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