[34-longterm 164/260] ALSA: rawmidi: fix oops (use after free) when unloading a driver module

[Paul Gortmaker]

From: Clemens Ladisch <clemens@xxxxxxxxxx>

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@xxxxxxxxxx>
Reported-by: Krzysztof Foltman <wdev@xxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 sound/core/rawmidi.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 0f5a194..5fac1a3 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -531,13 +531,15 @@ 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;
 }
 
-- 
1.7.3.3

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