[PATCH 3.10 122/139] ALSA: core: Fix unexpected error at replacing user TLV

[Willy Tarreau]

From: Takashi Iwai <tiwai@xxxxxxx>

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")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 sound/core/control.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/core/control.c b/sound/core/control.c
index 251bc57..c392826 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1088,7 +1088,7 @@ static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol,
 		mutex_lock(&ue->card->user_ctl_lock);
 		change = ue->tlv_data_size != size;
 		if (!change)
-			change = memcmp(ue->tlv_data, new_data, size);
+			change = memcmp(ue->tlv_data, new_data, size) != 0;
 		kfree(ue->tlv_data);
 		ue->tlv_data = new_data;
 		ue->tlv_data_size = size;
-- 
2.8.0.rc2.1.gbe9624a