From 5bb5cc4ec4fa756070edf5e851fa9607dbf6d3a8 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Tue, 22 Aug 2017 08:15:13 +0200
Subject: [PATCH] ALSA: core: Fix unexpected error at replacing user TLV

commit 88c54cdf61f508ebcf8da2d819f5dfc03e954d1d upstream.

When user tries to replace the user-defined control TLV, the kernel
checks the change of its content via memcmp().  The problem is that
the kernel passes the return value from memcmp() as is.  memcmp()
gives a non-zero negative value depending on the comparison result,
and this shall be recognized as an error code.

The patch covers that corner-case, return 1 properly for the changed
TLV.

Fixes: 8aa9b586e420 ("[ALSA] Control API - more robust TLV implementation")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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