From: Johan Hovold <johan@kernel.org>
Date: Wed, 30 Jan 2019 09:49:34 +0000 (+0100)
Subject: staging: speakup: fix tty-operation NULL derefs
X-Git-Tag: Ubuntu-4.15.0-61.68~3373
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=387e0393d4605087cb20d6c3aff22375649b582c;p=mirror_ubuntu-bionic-kernel.git

staging: speakup: fix tty-operation NULL derefs

BugLink: https://bugs.launchpad.net/bugs/1837664

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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
---

diff --git a/drivers/staging/speakup/spk_ttyio.c b/drivers/staging/speakup/spk_ttyio.c
index 513cebbd161c..a25df41b7245 100644
--- a/drivers/staging/speakup/spk_ttyio.c
+++ b/drivers/staging/speakup/spk_ttyio.c
@@ -245,7 +245,8 @@ 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);
 }
 
@@ -257,7 +258,8 @@ 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);
 }