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Date: Mon, 10 Oct 2022 19:02:46 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Mushahid Hussain <mushi.shar@...il.com>
Cc: samuel.thibault@...-lyon.org, speakup@...ux-speakup.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Speakup: fix a segfault caused by switching consoles
On Mon, Oct 10, 2022 at 09:57:20PM +0500, Mushahid Hussain wrote:
> This patch fixes a segfault by adding a null check on synth in
> speakup_con_update(). The segfault can be reproduced as follows:
>
> - Login into a text console
>
> - Load speakup and speakup_soft modules
>
> - Remove speakup_soft
>
> - Switch to a graphics console
>
> This is caused by lack of a null check on `synth` in
> speakup_con_update().
>
> Here's the sequence that causes the segfault:
>
> - When we remove the speakup_soft, synth_release() sets the synth
> to null.
>
> - After that, when we change the virtual console to graphics
> console, vt_notifier_call() is fired, which then calls
> speakup_con_update().
>
> - Inside speakup_con_update() there's no null check on synth,
> so it calls synth_printf().
>
> - Inside synth_printf(), synth_buffer_add() and synth_start(),
> both access synth, when it is null and causing a segfault.
>
> Therefore adding a null check on synth solves the issue.
>
> Signed-off-by: Mushahid Hussain <mushi.shar@...il.com>
> Signed-off-by: Samuel Thibault <samuel.thibault@...-lyon.org>
> ---
> drivers/accessibility/speakup/main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
What commit id does this fix? Should it go to stable kernels?
thanks,
greg k-h
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