{"id":"CVE-2025-68372","summary":"nbd: defer config put in recv_work","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnbd: defer config put in recv_work\n\nThere is one uaf issue in recv_work when running NBD_CLEAR_SOCK and\nNBD_CMD_RECONFIGURE:\n  nbd_genl_connect     // conf_ref=2 (connect and recv_work A)\n  nbd_open\t       // conf_ref=3\n  recv_work A done     // conf_ref=2\n  NBD_CLEAR_SOCK       // conf_ref=1\n  nbd_genl_reconfigure // conf_ref=2 (trigger recv_work B)\n  close nbd\t       // conf_ref=1\n  recv_work B\n    config_put         // conf_ref=0\n    atomic_dec(&config-\u003erecv_threads); -\u003e UAF\n\nOr only running NBD_CLEAR_SOCK:\n  nbd_genl_connect   // conf_ref=2\n  nbd_open \t     // conf_ref=3\n  NBD_CLEAR_SOCK     // conf_ref=2\n  close nbd\n    nbd_release\n      config_put     // conf_ref=1\n  recv_work\n    config_put \t     // conf_ref=0\n    atomic_dec(&config-\u003erecv_threads); -\u003e UAF\n\nCommit 87aac3a80af5 (\"nbd: call nbd_config_put() before notifying the\nwaiter\") moved nbd_config_put() to run before waking up the waiter in\nrecv_work, in order to ensure that nbd_start_device_ioctl() would not\nbe woken up while nbd-\u003etask_recv was still uncleared.\n\nHowever, in nbd_start_device_ioctl(), after being woken up it explicitly\ncalls flush_workqueue() to make sure all current works are finished.\nTherefore, there is no need to move the config put ahead of the wakeup.\n\nMove nbd_config_put() to the end of recv_work, so that the reference is\nheld for the whole lifetime of the worker thread. This makes sure the\nconfig cannot be freed while recv_work is still running, even if clear\n+ reconfigure interleave.\n\nIn addition, we don't need to worry about recv_work dropping the last\nnbd_put (which causes deadlock):\n\npath A (netlink with NBD_CFLAG_DESTROY_ON_DISCONNECT):\n  connect  // nbd_refs=1 (trigger recv_work)\n  open nbd // nbd_refs=2\n  NBD_CLEAR_SOCK\n  close nbd\n    nbd_release\n      nbd_disconnect_and_put\n        flush_workqueue // recv_work done\n      nbd_config_put\n        nbd_put // nbd_refs=1\n      nbd_put // nbd_refs=0\n        queue_work\n\npath B (netlink without NBD_CFLAG_DESTROY_ON_DISCONNECT):\n  connect  // nbd_refs=2 (trigger recv_work)\n  open nbd // nbd_refs=3\n  NBD_CLEAR_SOCK // conf_refs=2\n  close nbd\n    nbd_release\n      nbd_config_put // conf_refs=1\n      nbd_put // nbd_refs=2\n  recv_work done // conf_refs=0, nbd_refs=1\n  rmmod // nbd_refs=0\n\nDepends-on: e2daec488c57 (\"nbd: Fix hungtask when nbd_config_put\")","modified":"2026-04-02T13:03:36.783507Z","published":"2025-12-24T10:33:02.679Z","related":["SUSE-SU-2026:0447-1","SUSE-SU-2026:0472-1","SUSE-SU-2026:0473-1","SUSE-SU-2026:0587-1","SUSE-SU-2026:20477-1","SUSE-SU-2026:20498-1","SUSE-SU-2026:20555-1","SUSE-SU-2026:20599-1","SUSE-SU-2026:20615-1","SUSE-SU-2026:20845-1","SUSE-SU-2026:20876-1","openSUSE-SU-2026:10039-1","openSUSE-SU-2026:10301-1","openSUSE-SU-2026:20287-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68372.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/198aa230a6f8c1f6af7ed26b29180749c3e79e4d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1ba2ced2bbdf7e64a30c3e88c70ea8bc208d1509"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3692884bd6187d89d41eef81e5a9724519fd01c1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/443a1721806b6ff6303b5229e9811d68172d622f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6b69593f72e1bfba6ca47ca8d9b619341fded7d6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/742012f6bf29553fdc460bf646a58df3a7b43d01"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9517b82d8d422d426a988b213fdd45c6b417b86d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d3ba312675911ff9e3fefefd551751e153a9f0a9"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68372.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-68372"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"87aac3a80af5cbad93e63250e8a1e19095ba0d30"},{"fixed":"198aa230a6f8c1f6af7ed26b29180749c3e79e4d"},{"fixed":"d3ba312675911ff9e3fefefd551751e153a9f0a9"},{"fixed":"3692884bd6187d89d41eef81e5a9724519fd01c1"},{"fixed":"1ba2ced2bbdf7e64a30c3e88c70ea8bc208d1509"},{"fixed":"6b69593f72e1bfba6ca47ca8d9b619341fded7d6"},{"fixed":"443a1721806b6ff6303b5229e9811d68172d622f"},{"fixed":"742012f6bf29553fdc460bf646a58df3a7b43d01"},{"fixed":"9517b82d8d422d426a988b213fdd45c6b417b86d"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"0a4e383fc3aa6540f804c4fd1184a96ae5de6ef8"},{"last_affected":"2ef6f4bd60411934e3fc2715442c2afe70f84bf3"},{"last_affected":"742fd49cf811ca164489e339b862e3fb8e240a73"},{"last_affected":"14df8724aeeef338172e2a2d6efadc989921ca0f"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-68372.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.10.0"},{"fixed":"5.10.248"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.198"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.160"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.120"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.63"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.17.13"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.18.0"},{"fixed":"6.18.2"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-68372.json"}}],"schema_version":"1.7.5"}