ALSA: firewire-lib: add buffer-over-run protection at receiving more data blocks than expected
In IEC 61883-6, the number of data blocks in a packet is limited up to
the value of SYT_INTERVAL. Current implementation is compliant to the
limitation, while it can cause buffer-over-run when the value of dbs
field in received packet is illegally large.
This commit adds a validator to detect such illegal packets to prevent
the buffer-over-run. Actually, the buffer is aligned to the size of memory
page, thus this issue hardly causes system errors due to the room to page
alignment, as long as a few packets includes such jumbo payload; i.e.
a packet to several received packets.
Here, Behringer F-Control Audio 202 (based on OXFW 960) has a quirk to
postpone transferring isochronous packet till finish handling any
asynchronous packets. In this case, this model is lazy, transfers no
packets according to several cycle-start packets. After finishing, this
model pushes required data in next isochronous packet. As a result, the
packet include more data blocks than IEC 61883-6 defines.
To continue to support this model, this commit adds a new flag to extend
the length of calculated payload. This flag allows the size of payload
5 times as large as IEC 61883-6 defines. As a result, packets from this
model passed the validator successfully.
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/firewire/amdtp.h b/sound/firewire/amdtp.h
index 8a03a91..26b9093 100644
--- a/sound/firewire/amdtp.h
+++ b/sound/firewire/amdtp.h
@@ -29,6 +29,9 @@
* packet is not continuous from an initial value.
* @CIP_EMPTY_HAS_WRONG_DBC: Only for in-stream. The value of dbc in empty
* packet is wrong but the others are correct.
+ * @CIP_JUMBO_PAYLOAD: Only for in-stream. The number of data blocks in an
+ * packet is larger than IEC 61883-6 defines. Current implementation
+ * allows 5 times as large as IEC 61883-6 defines.
*/
enum cip_flags {
CIP_NONBLOCKING = 0x00,
@@ -40,6 +43,7 @@
CIP_SKIP_DBC_ZERO_CHECK = 0x20,
CIP_SKIP_INIT_DBC_CHECK = 0x40,
CIP_EMPTY_HAS_WRONG_DBC = 0x80,
+ CIP_JUMBO_PAYLOAD = 0x100,
};
/**