69 lines
2.0 KiB
Diff
69 lines
2.0 KiB
Diff
From: Anton Blanchard <anton@samba.org>
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Date: Tue, 6 Apr 2010 11:42:38 +0000 (+1000)
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Subject: hvc_console: Fix race between hvc_close and hvc_remove
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X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=320718ee074acce5ffced6506cb51af1388942aa
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hvc_console: Fix race between hvc_close and hvc_remove
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I don't claim to understand the tty layer, but it seems like hvc_open and
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hvc_close should be balanced in their kref reference counting.
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Right now we get a kref every call to hvc_open:
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if (hp->count++ > 0) {
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tty_kref_get(tty); <----- here
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spin_unlock_irqrestore(&hp->lock, flags);
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hvc_kick();
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return 0;
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} /* else count == 0 */
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tty->driver_data = hp;
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hp->tty = tty_kref_get(tty); <------ or here if hp->count was 0
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But hvc_close has:
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tty_kref_get(tty);
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if (--hp->count == 0) {
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...
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/* Put the ref obtained in hvc_open() */
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tty_kref_put(tty);
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...
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}
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tty_kref_put(tty);
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Since the outside kref get/put balance we only do a single kref_put when
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count reaches 0.
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The patch below changes things to call tty_kref_put once for every
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hvc_close call, and with that my machine boots fine.
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Signed-off-by: Anton Blanchard <anton@samba.org>
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Acked-by: Amit Shah <amit.shah@redhat.com>
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Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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---
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diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
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index d3890e8..35cca4c 100644
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--- a/drivers/char/hvc_console.c
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+++ b/drivers/char/hvc_console.c
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@@ -368,16 +368,12 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
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hp = tty->driver_data;
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spin_lock_irqsave(&hp->lock, flags);
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- tty_kref_get(tty);
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if (--hp->count == 0) {
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/* We are done with the tty pointer now. */
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hp->tty = NULL;
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spin_unlock_irqrestore(&hp->lock, flags);
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- /* Put the ref obtained in hvc_open() */
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- tty_kref_put(tty);
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-
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if (hp->ops->notifier_del)
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hp->ops->notifier_del(hp, hp->data);
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