{"id":"CVE-2026-64112","summary":"rbd: eliminate a race in lock_dwork draining on unmap","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nrbd: eliminate a race in lock_dwork draining on unmap\n\nGiven how rbd_lock_add_request() and rbd_img_exclusive_lock() are\nwritten, lock_dwork may be (re)queued more than it's actually needed:\nfor example in case a new I/O request comes in while we are in the\nmiddle of rbd_acquire_lock() on behalf of another I/O request.  This is\nexpected and with rbd_release_lock() preemptively canceling lock_dwork\nis benign under normal operation.\n\nA more problematic example is maybe_kick_acquire():\n\n    if (have_requests || delayed_work_pending(&rbd_dev-\u003elock_dwork)) {\n            dout(\"%s rbd_dev %p kicking lock_dwork\\n\", __func__, rbd_dev);\n            mod_delayed_work(rbd_dev-\u003etask_wq, &rbd_dev-\u003elock_dwork, 0);\n    }\n\nIt's not unrealistic for lock_dwork to get canceled right after\ndelayed_work_pending() returns true and for mod_delayed_work() to\nrequeue it right there anyway.  This is a classic TOCTOU race.\n\nWhen it comes to unmapping the image, there is an implicit assumption\nof no self-initiated exclusive lock activity past the point of return\nfrom rbd_dev_image_unlock() which unlocks the lock if it happens to be\nheld.  This unlock is assumed to be final and lock_dwork (as well as\nall other exclusive lock tasks, really) isn't expected to get queued\nagain.  However, lock_dwork is canceled only in cancel_tasks_sync()\n(i.e. later in the unmap sequence) and on top of that the cancellation\ncan get in effect nullified by maybe_kick_acquire().  This may result\nin rbd_acquire_lock() executing after rbd_dev_device_release() and\nrbd_dev_image_release() run and free and/or reset a bunch of things.\nOne of the possible failure modes then is a violated\n\n    rbd_assert(rbd_image_format_valid(rbd_dev-\u003eimage_format));\n\nin rbd_dev_header_info() which is called via rbd_dev_refresh() from\nrbd_post_acquire_action().\n\nRedo exclusive lock task draining to provide saner semantics and try\nto meet the assumptions around rbd_dev_image_unlock().","modified":"2026-07-22T03:32:04.300398625Z","published":"2026-07-19T15:40:13.652Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64112.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/3427d7ae38337066ce88b68302e285d344ab756b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9400efc76b42c751211974a25c91d2c19c65b01b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9dcd4f5c99b491c37be90b0bd9988db48225fb75"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9fc75b71fdd38465c76c6f6a884cdd4ae3c72d90"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64112.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64112"},{"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":"fd22aef8b47cfc068448df65c1183698b0abd815"},{"fixed":"3427d7ae38337066ce88b68302e285d344ab756b"},{"fixed":"9dcd4f5c99b491c37be90b0bd9988db48225fb75"},{"fixed":"9400efc76b42c751211974a25c91d2c19c65b01b"},{"fixed":"9fc75b71fdd38465c76c6f6a884cdd4ae3c72d90"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64112.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.12.0"},{"fixed":"6.12.92"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.34"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.11"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64112.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}