staging: speakup: fix async usb removal

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When an external USB synth is unplugged while the module is loaded, we
get a null pointer deref. This is because the tty disappears while
speakup tries to use to to communicate with the synth. This patch fixes
it by checking tty for null before using it. Since tty can become null
between the check and its usage, a mutex is introduced. tty usage is
now surrounded by the mutex, as is the code in speakup_ldisc_close which
sets the tty to null. The mutex also serialises calls to tty from
speakup code.

In case of tty being null, this sets synth->alive to zero and restarts
ttys in case they were stopped by speakup.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Okash Khawaja 2017-08-12 09:05:47 +01:00 • committed by Greg Kroah-Hartman

parent 043a2e7520

commit f5bee24d86

1 changed files with 50 additions and 0 deletions

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drivers/staging/speakup/spk_ttyio.c

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