ksmbd: fix use-after-free of a deferred file_lock on SMB2_CLOSE then SMB2_CANCEL
Summary
| CVE | CVE-2026-64437 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-25 10:17:28 UTC |
| Updated | 2026-07-25 10:17:28 UTC |
| Description | In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of a deferred file_lock on SMB2_CLOSE then SMB2_CANCEL Commit f580d27e8928 ("ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL") made smb2_cancel() skip a work whose state is KSMBD_WORK_CANCELLED, so its cancel_fn cannot be fired a second time. But KSMBD_WORK has three states (ACTIVE, CANCELLED, CLOSED), and the same freeing producer path is reached for CLOSED too: SMB2_CLOSE on the locking handle -> set_close_state_blocked_works() sets the deferred work's state to KSMBD_WORK_CLOSED and wakes the smb2_lock() worker. The worker takes the non-ACTIVE early-exit, locks_free_lock()s the file_lock and, because the state is not KSMBD_WORK_CANCELLED, takes the STATUS_RANGE_NOT_LOCKED branch with "goto out2" -- which, like the cancelled branch, skips release_async_work(). The work stays on conn->async_requests with a live cancel_fn = smb2_remove_blocked_lock pointing at the freed file_lock. A subsequent SMB2_CANCEL for the same AsyncId then passes the KSMBD_WORK_CANCELLED-only guard (its state is KSMBD_WORK_CLOSED), so smb2_cancel() fires cancel_fn again over the freed file_lock -- the same use-after-free fixed, via SMB2_CLOSE instead of a first SMB2_CANCEL: BUG: KASAN: slab-use-after-free in __locks_delete_block __locks_delete_block locks_delete_block ksmbd_vfs_posix_lock_unblock smb2_remove_blocked_lock smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn handle_ksmbd_work Allocated by ...: locks_alloc_lock <- smb2_lock Freed by ...: locks_free_lock <- smb2_lock (non-ACTIVE early-exit) ... cache file_lock_cache of size 192 Reproduced on mainline 7.1-rc7 (which already contains f580d27e8928) with KASAN by an authenticated SMB client; the double-SMB2_CANCEL control is silent on that kernel, so the splat is attributable to the CLOSE trigger. Only an ACTIVE deferred work may have its cancel_fn fired: both terminal states (CANCELLED and CLOSED) reach the smb2_lock() early-exit that frees the file_lock and skips release_async_work(). Guard on KSMBD_WORK_ACTIVE so any non-active work is skipped. |
Risk And Classification
EPSS: 0.002150000 probability, percentile 0.119910000 (date 2026-07-25)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected b7063c7426ea5a4d15e01b60538718765392f49d a796ba4e61d5e14e07b79a359faac69f8f9b22a3 git | Not specified |
| CNA | Linux | Linux | affected 0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd b8e274e69ab09222c7a552c7c0c1eef9ce627fc1 git | Not specified |
| CNA | Linux | Linux | affected 89ae9df09d2c1fb4a4eb495c113a7ce1dca34147 ddb9239828336b36d8a3ef5943fdffb2f55b6508 git | Not specified |
| CNA | Linux | Linux | affected 14d2eee0193ac3cd1bf3d014373449f0b8d35d6d 94083db751930b1540ddff2b54d4677549c57f81 git | Not specified |
| CNA | Linux | Linux | affected f580d27e8928828693df44ba2db0fffdbe11dfea 12c36c99655f325befe50c26842f7deca414c381 git | Not specified |
| CNA | Linux | Linux | affected f580d27e8928828693df44ba2db0fffdbe11dfea 10f293a07f9e10e988b0ae44e2e99c631f5a68e0 git | Not specified |
| CNA | Linux | Linux | affected 2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694 git | Not specified |
| CNA | Linux | Linux | affected 6.1.176 6.1.178 semver | Not specified |
| CNA | Linux | Linux | affected 6.6.143 6.6.145 semver | Not specified |
| CNA | Linux | Linux | affected 6.12.94 6.12.96 semver | Not specified |
| CNA | Linux | Linux | affected 6.18.36 6.18.39 semver | Not specified |
| CNA | Linux | Linux | affected 7.0.13 7.1 semver | Not specified |
| CNA | Linux | Linux | affected 7.1 | Not specified |
| CNA | Linux | Linux | unaffected 7.1 semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.178 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.145 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.96 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.39 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1.4 7.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2-rc1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/94083db751930b1540ddff2b54d4677549c57f81 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/b8e274e69ab09222c7a552c7c0c1eef9ce627fc1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/10f293a07f9e10e988b0ae44e2e99c631f5a68e0 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/12c36c99655f325befe50c26842f7deca414c381 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/ddb9239828336b36d8a3ef5943fdffb2f55b6508 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/a796ba4e61d5e14e07b79a359faac69f8f9b22a3 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.