From 0fc801f8018000c8e64a275a20cb1da7c54e46df Mon Sep 17 00:00:00 2001 From: Mushahid Hussain Date: Mon, 10 Oct 2022 21:57:20 +0500 Subject: speakup: fix a segfault caused by switching consoles 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 Signed-off-by: Mushahid Hussain Signed-off-by: Samuel Thibault Link: https://lore.kernel.org/r/20221010165720.397042-1-mushi.shar@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/accessibility/speakup/main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/accessibility') 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 */ -- cgit