[PATCH v2 1/2] ALSA: ump: Don't accept an invalid UMP protocol number

[Takashi Iwai <tiwai@suse.de>]

When a UMP Stream Configuration message is received, the driver tries
to switch the protocol, but there was no sanity check of the protocol,
hence it can pass an invalid value.  Add the check and bail out if a
wrong value is passed.

Fixes: a79807683781 ("ALSA: ump: Add helper to change MIDI protocol")
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
v1->v2: Fix the line dropped mistakenly in v1 patch

 sound/core/ump.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sound/core/ump.c b/sound/core/ump.c
index fd6a68a54278..117c7ecc4856 100644
--- a/sound/core/ump.c
+++ b/sound/core/ump.c
@@ -685,10 +685,17 @@ static void seq_notify_protocol(struct snd_ump_endpoint *ump)
  */
 int snd_ump_switch_protocol(struct snd_ump_endpoint *ump, unsigned int protocol)
 {
+	unsigned int type;
+
 	protocol &= ump->info.protocol_caps;
 	if (protocol == ump->info.protocol)
 		return 0;
 
+	type = protocol & SNDRV_UMP_EP_INFO_PROTO_MIDI_MASK;
+	if (type != SNDRV_UMP_EP_INFO_PROTO_MIDI1 &&
+	    type != SNDRV_UMP_EP_INFO_PROTO_MIDI2)
+		return 0;
+
 	ump->info.protocol = protocol;
 	ump_dbg(ump, "New protocol = %x (caps = %x)\n",
 		protocol, ump->info.protocol_caps);
-- 
2.43.0