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    SubjectRe: [PATCH] tty: add lockdep annotations
    > Yes, tty->driver deref is ok (tty points to valid memory), but crash is
    > on tty->driver->ops (driver points to freed/illegal memory)
    >
    > using slub_debug=FZPU, I can indeed see RDI=6b6b6b6b6b6b6b6b

    driver and driver->ops is basically const and it's not what you'd expect
    from a tty refcount bug. The driver side puts shouldn't have changed but
    I'll take a look over that patch and the error paths closely again just
    in case.

    It could be that tty->driver is pointing at a valid but bogus location
    but again its not something I'd expect.

    > By the way, release_one_tty() uses the following racy code :
    >
    > tty_driver_kref_put(driver);
    > module_put(driver->owner);
    >
    > I would use following patch to make sure bad things cant happen...

    Agreed. Although we wouldn't be unloading console or pty so it's alas not
    the real cause.


    Alan


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