Bug 2460681 (CVE-2026-31477)

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix memory leaks and NULL deref in smb2_lock()

smb2_lock() has three error handling issues after list_del() detaches
smb_lock from lock_list at no_check_cl:

1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK
   path, goto out leaks smb_lock and its flock because the out:
   handler only iterates lock_list and rollback_list, neither of
   which contains the detached smb_lock.

2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out
   leaks smb_lock and flock for the same reason.  The error code
   returned to the dispatcher is also stale.

3) In the rollback path, smb_flock_init() can return NULL on
   allocation failure.  The result is dereferenced unconditionally,
   causing a kernel NULL pointer dereference.  Add a NULL check to
   prevent the crash and clean up the bookkeeping; the VFS lock
   itself cannot be rolled back without the allocation and will be
   released at file or connection teardown.

Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before
the if(!rc) check in the UNLOCK branch so all exit paths share one
free site, and by freeing smb_lock and flock before goto out in the
non-UNLOCK branch.  Propagate the correct error code in both cases.
Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding
a NULL check for locks_free_lock(rlock) in the shared cleanup.

Found via call-graph analysis using sqry.