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: sta...@vger.kernel.org
Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()")
Signed-off-by: Michał Mirosław <mirq-li...@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

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