Messages in this thread Patch in this message | | | From | Mushahid Hussain <> | Subject | [PATCH] Speakup: fix a segfault caused by switching consoles | Date | Mon, 10 Oct 2022 21:57:20 +0500 |
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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.
Signed-off-by: Mushahid Hussain <mushi.shar@gmail.com> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org> --- 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 */ -- 2.38.0
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