From: Mushahid Hussain mushi.shar@gmail.com
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@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 --- drivers/accessibility/speakup/main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/accessibility/speakup/main.c +++ b/drivers/accessibility/speakup/main.c @@ -1780,7 +1780,7 @@ 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 */