Bug 2516299 (CVE-2026-72381) - CVE-2026-72381 kernel: ksmbd: fix use-after-free of fp->owner.name in durable handle owner check
Summary: CVE-2026-72381 kernel: ksmbd: fix use-after-free of fp->owner.name in durable...
Keywords:
Status: NEW
Alias: CVE-2026-72381
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-15 06:05 UTC by OSIDB Bzimport
Modified: 2026-08-18 06:05 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
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Description OSIDB Bzimport 2026-08-15 06:05:14 UTC
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix use-after-free of fp->owner.name in durable handle owner check

Two concurrent SMB2 durable reconnects (DH2C/DHnC) on the same
persistent_id race the fp->owner.name compare-read in
ksmbd_vfs_compare_durable_owner() against the kfree() in
ksmbd_reopen_durable_fd()'s reopen-success path. fp->owner.name is a
standalone kstrdup() buffer whose lifetime is independent of the fp
refcount, and the two sites share no lock: the compare reads the buffer
while the reopen frees it, so the strcmp() can dereference freed memory.

Commit 7ce4fc40018d ("ksmbd: fix durable reconnect double-bind race in
ksmbd_reopen_durable_fd") made the fp->conn claim atomic under
global_ft.lock (closing the owner.name double-free and the ksmbd_file
write-UAF), but the compare-read versus reopen-free pair was left
unserialized.

  BUG: KASAN: slab-use-after-free in strcmp+0x2c/0x80
  Read of size 1 by task kworker
    strcmp
    ksmbd_vfs_compare_durable_owner
    smb2_check_durable_oplock
    smb2_open
  Freed by task kworker:
    kfree
    ksmbd_reopen_durable_fd
    smb2_open
  Allocated by task kworker:
    kstrdup
    session_fd_check
    smb2_session_logoff
  The buggy address belongs to the cache kmalloc-8

Serialize both sides of the race with fp->f_lock.  The global durable
file-table lock still protects the durable reconnect claim, but
fp->owner.name is per-open state and does not need to block unrelated
durable table lookups or reconnects.  The teardown is left at its
existing location after the reopen-success point so that an __open_id()
rollback still retains owner.name for a later legitimate reconnect to
verify.


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