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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 1/2] ALSA: pcm: disallow linking stream to itself
Date: Mon, 08 Jun 2020 12:06:32 +0200
Message-ID: <dc38ec162b8c83e53cf48cc8dc4dbac78667e394.1591610330.git.mirq-linux@rere.qmqm.pl> (raw)
In-Reply-To: <cover.1591610329.git.mirq-linux@rere.qmqm.pl>

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


  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-08 10:06 [PATCH 0/2] ALSA: pcm: stream linking locking fixes Michał Mirosław
2020-06-08 10:06 ` Michał Mirosław [this message]
2020-06-08 12:48   ` [PATCH 1/2] ALSA: pcm: disallow linking stream to itself Takashi Iwai
2020-06-08 16:50     ` [PATCH v2] " Michał Mirosław
2020-06-08 17:35       ` Takashi Iwai
2020-06-08 10:06 ` [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat Michał Mirosław
2020-06-08 13:02   ` Takashi Iwai

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