This is a note to let you know that I've just added the patch titled speakup: fix a segfault caused by switching consoles to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: speakup-fix-a-segfault-caused-by-switching-consoles.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 0fc801f8018000c8e64a275a20cb1da7c54e46df Mon Sep 17 00:00:00 2001 From: Mushahid Hussain <mushi.shar@xxxxxxxxx> Date: Mon, 10 Oct 2022 21:57:20 +0500 Subject: speakup: fix a segfault caused by switching consoles From: Mushahid Hussain <mushi.shar@xxxxxxxxx> commit 0fc801f8018000c8e64a275a20cb1da7c54e46df upstream. 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@xxxxxxxxxx> Signed-off-by: Mushahid Hussain <mushi.shar@xxxxxxxxx> Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20221010165720.397042-1-mushi.shar@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/staging/speakup/main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/staging/speakup/main.c +++ b/drivers/staging/speakup/main.c @@ -1778,7 +1778,7 @@ static void speakup_con_update(struct 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 */ Patches currently in stable-queue which might be from mushi.shar@xxxxxxxxx are queue-4.19/speakup-fix-a-segfault-caused-by-switching-consoles.patch