CVE-2025-21731
Description
In the Linux kernel, the following vulnerability has been resolved: nbd: don't allow reconnect after disconnect Following process can cause nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.
How to fix
- linux linux_kernel5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, 6.12.13, 6.13.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| linux linux_kernel | 4.12 ≤ v < 5.4.291, 5.5 ≤ v < 5.10.235, 5.11 ≤ v < 5.15.179, 5.16 ≤ v < 6.1.129, 6.2 ≤ v < 6.6.76, 6.7 ≤ v < 6.12.13, 6.13 ≤ v < 6.13.2 | 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, 6.12.13, 6.13.2 |
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