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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        =?UTF-8?q?Micha=C5=82=20Miros=C5=82aw?= <mirq-linux@rere.qmqm.pl>,
        Takashi Iwai <tiwai@suse.de>
Subject: [PATCH 4.9 024/128] ALSA: pcm: disallow linking stream to itself
Date:   Fri, 19 Jun 2020 16:31:58 +0200
Message-Id: <20200619141621.457414340@linuxfoundation.org>
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From: Michał Mirosław <mirq-linux@rere.qmqm.pl>

commit 951e2736f4b11b58dc44d41964fa17c3527d882a upstream.

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>
Link: https://lore.kernel.org/r/89c4a2487609a0ed6af3ecf01cc972bdc59a7a2d.1591634956.git.mirq-linux@rere.qmqm.pl
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
 sound/core/pcm_native.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -1836,6 +1836,11 @@ static int snd_pcm_link(struct snd_pcm_s
 	}
 	pcm_file = f.file->private_data;
 	substream1 = pcm_file->substream;
+	if (substream == substream1) {
+		res = -EINVAL;
+		goto _badf;
+	}
+
 	group = kmalloc(sizeof(*group), GFP_KERNEL);
 	if (!group) {
 		res = -ENOMEM;