From 0fc801f8018000c8e64a275a20cb1da7c54e46df Mon Sep 17 00:00:00 2001
From: Mushahid Hussain <mushi.shar@gmail.com>
Date: Mon, 10 Oct 2022 21:57:20 +0500
Subject: [PATCH] speakup: fix a segfault caused by switching consoles
Git-commit: 0fc801f8018000c8e64a275a20cb1da7c54e46df
Patch-mainline: v6.1-rc6
References: git-fixes
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.
Fixes: 2610df41489f ("staging: speakup: Add pause command used on switching to graphical mode")
Cc: stable <stable@kernel.org>
Signed-off-by: Mushahid Hussain <mushi.shar@gmail.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20221010165720.397042-1-mushi.shar@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/accessibility/speakup/main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/accessibility/speakup/main.c b/drivers/accessibility/speakup/main.c
index f52265293482..73db0cb44fc7 100644
--- a/drivers/accessibility/speakup/main.c
+++ b/drivers/accessibility/speakup/main.c
@@ -1778,7 +1778,7 @@ static void speakup_con_update(struct vc_data *vc)
{
unsigned long flags;
- if (!speakup_console[vc->vc_num] || spk_parked)
+ if (!speakup_console[vc->vc_num] || spk_parked || !synth)
return;
if (!spin_trylock_irqsave(&speakup_info.spinlock, flags))
/* Speakup output, discard */
--
2.35.3