[PATCH 5.15 124/181] speakup: fix a segfault caused by switching consoles

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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/accessibility/speakup/main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/accessibility/speakup/main.c
+++ b/drivers/accessibility/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 */





[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux