CVE-2026-68312: cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths

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

cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths

In cifsclosedeferredfile(), cifsclosealldeferredfiles(), and cifsclosedeferredfileunderdentry(), when a pending deferred close is cancelled via canceldelayedwork(), the subsequent kmallocobj() to add the file to the local processing list may fail under memory pressure. The loop breaks immediately, but the cancelled work is no longer pending (it would have called cifsFileInfoput()), and the cfile is never added to filehead for processing. The cifsFileInfo reference and the open server handle both leak.

Fix by saving the cfile that failed allocation in a local variable, breaking as before, and calling cifsFileInfoput() on it after releasing the lock. Any files later in the iteration are unaffected since their deferred work is still pending and will fire normally.