[PATCH] staging: speakup: fix tty-operation NULL derefs

[PATCH] staging: speakup: fix tty-operation NULL derefs

[Johan Hovold]

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

diff --git a/drivers/staging/speakup/spk_ttyio.c b/drivers/staging/speakup/spk_ttyio.c
index c92bbd05516e..005de0024dd4 100644
--- 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 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);
 }
 
-- 
2.20.1

Re: [PATCH] staging: speakup: fix tty-operation NULL derefs

[Samuel Thibault]

Johan Hovold, le mer. 30 janv. 2019 10:49:34 +0100, a ecrit:
> 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>

Indeed.

Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

> ---
>  drivers/staging/speakup/spk_ttyio.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/speakup/spk_ttyio.c b/drivers/staging/speakup/spk_ttyio.c
> index c92bbd05516e..005de0024dd4 100644
> --- 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 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);
>  }
>  
> -- 
> 2.20.1
> 

-- 
Samuel
R: Parce que ça renverse bêtement l'ordre naturel de lecture!
Q: Mais pourquoi citer en fin d'article est-il si effroyable?
R: Citer en fin d'article
Q: Quelle est la chose la plus désagréable sur les groupes de news?