{"id":"CVE-2026-64112","title":"rbd: eliminate a race in lock_dwork draining on unmap","summary":"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…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 3427d7ae38337066ce88b68302e285d344ab756b","Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 9dcd4f5c99b491c37be90b0bd9988db48225fb75","Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 9400efc76b42c751211974a25c91d2c19c65b01b","Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 9fc75b71fdd38465c76c6f6a884cdd4ae3c72d90","Linux 4.12"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:36:26.577928Z"},"published":"2026-07-19","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:42:22.660Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-64112","references":[{"url":"https://git.kernel.org/stable/c/3427d7ae38337066ce88b68302e285d344ab756b"},{"url":"https://git.kernel.org/stable/c/9dcd4f5c99b491c37be90b0bd9988db48225fb75"},{"url":"https://git.kernel.org/stable/c/9400efc76b42c751211974a25c91d2c19c65b01b"},{"url":"https://git.kernel.org/stable/c/9fc75b71fdd38465c76c6f6a884cdd4ae3c72d90"}],"tags":["cve.org"],"epss":0.00099,"epssPercentile":0.00785,"ingestedAt":"2026-10-16T17:24:46.805Z","slug":"CVE-2026-64112","body":"## Overview\n\nIn 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->lock_dwork)) {\n            dout(\"%s rbd_dev %p kicking lock_dwork\\n\", __func__, rbd_dev);\n            mod_delayed_work(rbd_dev->task_wq, &rbd_dev->lock_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->image_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().\n\n## Affected\n\n- `Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 3427d7ae38337066ce88b68302e285d344ab756b`\n- `Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 9dcd4f5c99b491c37be90b0bd9988db48225fb75`\n- `Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 9400efc76b42c751211974a25c91d2c19c65b01b`\n- `Linux >= fd22aef8b47cfc068448df65c1183698b0abd815 < 9fc75b71fdd38465c76c6f6a884cdd4ae3c72d90`\n- `Linux 4.12`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}