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staging: speakup: fix tty-operation NULL derefs

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commit a1960e0f1639cb1f7a3d94521760fc73091f6640 upstream.

The send_xchar() and tiocmset() tty operations are optional. Add the
missing sanity checks to prevent user-space triggerable NULL-pointer
dereferences.

Fixes: 6b9ad1c742bf ("staging: speakup: add send_xchar, tiocmset and input functionality for tty")
Cc: stable <stable@vger.kernel.org>     # 4.13
Cc: Okash Khawaja <okash.khawaja@gmail.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2019-01-30 10:49:34 +01:00 committed by Greg Kroah-Hartman
parent f8b500d109
commit 04f2d3f8be
1 changed files with 4 additions and 2 deletions
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6
drivers/staging/speakup/spk_ttyio.c
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@ -246,7 +246,8 @@ static void spk_ttyio_send_xchar(char ch)
return;
}
speakup_tty->ops->send_xchar(speakup_tty, ch);
if (speakup_tty->ops->send_xchar)
speakup_tty->ops->send_xchar(speakup_tty, ch);
mutex_unlock(&speakup_tty_mutex);
}
@ -258,7 +259,8 @@ static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear)
return;
}
speakup_tty->ops->tiocmset(speakup_tty, set, clear);
if (speakup_tty->ops->tiocmset)
speakup_tty->ops->tiocmset(speakup_tty, set, clear);
mutex_unlock(&speakup_tty_mutex);
}