linux-kernel - [34-longterm 006/196] ALSA: Fix yet another race in disconnection

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Message-Id: <1331597724-31358-7-git-send-email-paul.gortmaker@windriver.com>
Date:	Mon, 12 Mar 2012 20:12:14 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Takashi Iwai <tiwai@...e.de>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 006/196] ALSA: Fix yet another race in disconnection

From: Takashi Iwai <tiwai@...e.de>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit a45e3d6b13e97506b616980c0f122c3389bcefa4 upstream.

This patch fixes a race between snd_card_file_remove() and
snd_card_disconnect().  When the card is added to shutdown_files list
in snd_card_disconnect(), but it's freed in snd_card_file_remove() at
the same time, the shutdown_files list gets corrupted.  The list member
must be freed in snd_card_file_remove() as well.

Reported-and-tested-by: Russ Dill <russ.dill@...il.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 sound/core/init.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/core/init.c b/sound/core/init.c
index ec4a50c..82f350e 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -848,6 +848,7 @@ int snd_card_file_add(struct snd_card *card, struct file *file)
 		return -ENOMEM;
 	mfile->file = file;
 	mfile->disconnected_f_op = NULL;
+	INIT_LIST_HEAD(&mfile->shutdown_list);
 	spin_lock(&card->files_lock);
 	if (card->shutdown) {
 		spin_unlock(&card->files_lock);
@@ -883,6 +884,9 @@ int snd_card_file_remove(struct snd_card *card, struct file *file)
 	list_for_each_entry(mfile, &card->files_list, list) {
 		if (mfile->file == file) {
 			list_del(&mfile->list);
+			spin_lock(&shutdown_lock);
+			list_del(&mfile->shutdown_list);
+			spin_unlock(&shutdown_lock);
 			if (mfile->disconnected_f_op)
 				fops_put(mfile->disconnected_f_op);
 			found = mfile;
-- 
1.7.9.3

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