Re: [PATCH] tty: rpmsg: close port lookup-to-get race

[sashiko-bot@kernel.org]

> rpmsg_tty_install() obtains cport from tty_idr before taking a port
> reference. rpmsg_tty_destruct_port() removes the entry under idr_lock
> and frees cport. If channel removal drops the last reference between
> idr_find() and tty_port_get(), the install path dereferences freed
> memory.
> 
> The first-open path and channel removal can run concurrently. tty_mutex
> serializes TTY initialization, but rpmsg_tty_remove() does not take that
> mutex. tty_unregister_device() prevents later opens through cdev_del(),
> but cdev_del() does not wait for an open which has already entered the
> driver. Before rpmsg_tty_install() finishes, the port is not attached to
> the new TTY, so tty_port_tty_hangup() does not close this interval.
> 
> RPMsg channel removal may be initiated asynchronously by the remote
> processor or transport. In the test, the local process only needs
> [ ... ]
> Fixes: 7c0408d80579 ("tty: add rpmsg driver")
> Reported-by: Changyul Lee <lcy8047@gmail.com>
> Link: https://lore.kernel.org/all/179000811428.1227592.8003229121862460039.idr-bug-84@gmail.com/
> Assisted-by: LLM
> Signed-off-by: Sang-Hoon Choi <csh0052@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260923001647.1337001-1-csh0052@gmail.com?part=1