[PATCH v2] ALSA: pcm: disallow linking stream to itself

From: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
To: Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] ALSA: pcm: disallow linking stream to itself
Date: Mon, 08 Jun 2020 18:50:39 +0200	[thread overview]
Message-ID: <89c4a2487609a0ed6af3ecf01cc972bdc59a7a2d.1591634956.git.mirq-linux@rere.qmqm.pl> (raw)
In-Reply-To: <s5h4krl67vb.wl-tiwai@suse.de>

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>
---
v2: EDEADLK -> EINVAL
---
 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..434e7b604bad 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 = -EINVAL;
+		goto _badf;
+	}
+
 	group = kzalloc(sizeof(*group), GFP_KERNEL);
 	if (!group) {
 		res = -ENOMEM;
-- 
2.20.1

