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Date:   Mon, 08 Jun 2020 12:06:32 +0200
Message-Id: <dc38ec162b8c83e53cf48cc8dc4dbac78667e394.1591610330.git.mirq-linux@rere.qmqm.pl>
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From:   =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= <mirq-linux@rere.qmqm.pl>
Subject: [PATCH 1/2] ALSA: pcm: disallow linking stream to itself
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To:     Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>
Cc:     alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Prevent SNDRV_PCM_IOCTL_LINK linking stream to itself - the code
can't handle it. Fixed commit is not where bug was introduced, but
changes the context significantly.

Cc: stable@vger.kernel.org
Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
---
 sound/core/pcm_native.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index aef860256278..3ad399cb6f30 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -2166,6 +2166,12 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd)
 	}
 	pcm_file = f.file->private_data;
 	substream1 = pcm_file->substream;
+
+	if (substream == substream1) {
+		res = -EDEADLK;
+		goto _badf;
+	}
+
 	group = kzalloc(sizeof(*group), GFP_KERNEL);
 	if (!group) {
 		res = -ENOMEM;
-- 
2.20.1