From: Clemens Ladisch <clemens@ladisch.de>
Date: Fri, 15 Oct 2010 10:06:18 +0000 (+0200)
Subject: ALSA: rawmidi: fix oops (use after free) when unloading a driver module
X-Git-Tag: v2.6.32.25~60
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=28b4c9130be4377517c171f34cb9f0ba9f213f23;p=karo-tx-linux.git

ALSA: rawmidi: fix oops (use after free) when unloading a driver module

commit aa73aec6c385e2c797ac25cc7ccf0318031de7c8 upstream.

When a driver module is unloaded and the last still open file is a raw
MIDI device, the card and its devices will be actually freed in the
snd_card_file_remove() call when that file is closed.  Afterwards, rmidi
and rmidi->card point into freed memory, so the module pointer is likely
to be garbage.
(This was introduced by commit 9a1b64caac82aa02cb74587ffc798e6f42c6170a.)

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Reported-by: Krzysztof Foltman <wdev@foltman.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 70d6f25ba526..e4c12a1ee304 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -530,13 +530,15 @@ static int snd_rawmidi_release(struct inode *inode, struct file *file)
 {
 	struct snd_rawmidi_file *rfile;
 	struct snd_rawmidi *rmidi;
+	struct module *module;
 
 	rfile = file->private_data;
 	rmidi = rfile->rmidi;
 	rawmidi_release_priv(rfile);
 	kfree(rfile);
+	module = rmidi->card->module;
 	snd_card_file_remove(rmidi->card, file);
-	module_put(rmidi->card->module);
+	module_put(module);
 	return 0;
 }