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Subject[PATCH 4.20 335/352] staging: speakup: fix tty-operation NULL derefs
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@kernel.org>

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>

---
drivers/staging/speakup/spk_ttyio.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/staging/speakup/spk_ttyio.c
+++ b/drivers/staging/speakup/spk_ttyio.c
@@ -265,7 +265,8 @@ 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);
}

@@ -277,7 +278,8 @@ static void spk_ttyio_tiocmset(unsigned
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);
}


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