linux-kernel - [PATCH 11/61] ALSA: Dereference after free in snd_hwdep

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Date:	Tue, 31 Oct 2006 21:33:51 -0800
From:	Chris Wright <chrisw@...s-sol.org>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: [PATCH 11/61] ALSA: Dereference after free in snd_hwdep_release()

-stable review patch.  If anyone has any objections, please let us know.
------------------

From: Florin Malita <fmalita@...il.com>

[PATCH] ALSA: Dereference after free in snd_hwdep_release()

snd_card_file_remove() may free hw->card so we can't dereference
hw->card->module after that.

Coverity ID 1420.

This bug actually causes an Oops at usb-disconnection, especially
with CONFIG_PREEMPT.

From: Florin Malita <fmalita@...il.com>
Signed-off-by: Florin Malita <fmalita@...il.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Chris Wright <chrisw@...s-sol.org>

---
 sound/core/hwdep.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux-2.6.18.1.orig/sound/core/hwdep.c
+++ linux-2.6.18.1/sound/core/hwdep.c
@@ -158,6 +158,7 @@ static int snd_hwdep_release(struct inod
 {
 	int err = -ENXIO;
 	struct snd_hwdep *hw = file->private_data;
+	struct module *mod = hw->card->module;
 	mutex_lock(&hw->open_mutex);
 	if (hw->ops.release) {
 		err = hw->ops.release(hw, file);
@@ -167,7 +168,7 @@ static int snd_hwdep_release(struct inod
 		hw->used--;
 	snd_card_file_remove(hw->card, file);
 	mutex_unlock(&hw->open_mutex);
-	module_put(hw->card->module);
+	module_put(mod);
 	return err;
 }
 

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