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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>
This commit is contained in:
Takashi Sakamoto 2015-05-22 23:00:50 +09:00 committed by Takashi Iwai
parent 181a152a09
commit a2064710ba
3 changed files with 31 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
sound/firewire/amdtp.c
View File

@ -251,7 +251,12 @@ EXPORT_SYMBOL(amdtp_stream_set_parameters);
*/
unsigned int amdtp_stream_get_max_payload(struct amdtp_stream *s)
{
return 8 + s->syt_interval * s->data_block_quadlets * 4;
unsigned int multiplier = 1;
if (s->flags & CIP_JUMBO_PAYLOAD)
multiplier = 5;
return 8 + s->syt_interval * s->data_block_quadlets * 4 * multiplier;
}
EXPORT_SYMBOL(amdtp_stream_get_max_payload);
@ -807,12 +812,16 @@ static void in_stream_callback(struct fw_iso_context *context, u32 cycle,
void *private_data)
{
struct amdtp_stream *s = private_data;
unsigned int p, syt, packets, payload_quadlets;
unsigned int p, syt, packets;
unsigned int payload_quadlets, max_payload_quadlets;
__be32 *buffer, *headers = header;
/* The number of packets in buffer */
packets = header_length / IN_PACKET_HEADER_SIZE;
/* For buffer-over-run prevention. */
max_payload_quadlets = amdtp_stream_get_max_payload(s) / 4;
for (p = 0; p < packets; p++) {
if (s->packet_index < 0)
break;
@ -828,6 +837,14 @@ static void in_stream_callback(struct fw_iso_context *context, u32 cycle,
/* The number of quadlets in this packet */
payload_quadlets =
(be32_to_cpu(headers[p]) >> ISO_DATA_LENGTH_SHIFT) / 4;
if (payload_quadlets > max_payload_quadlets) {
dev_err(&s->unit->device,
"Detect jumbo payload: %02x %02x\n",
payload_quadlets, max_payload_quadlets);
s->packet_index = -1;
break;
}
handle_in_packet(s, payload_quadlets, buffer);
}

4
sound/firewire/amdtp.h
View File

@ -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 @@ enum cip_flags {
CIP_SKIP_DBC_ZERO_CHECK = 0x20,
CIP_SKIP_INIT_DBC_CHECK = 0x40,
CIP_EMPTY_HAS_WRONG_DBC = 0x80,
CIP_JUMBO_PAYLOAD = 0x100,
};
/**

10
sound/firewire/oxfw/oxfw-stream.c
View File

@ -232,9 +232,15 @@ int snd_oxfw_stream_init_simplex(struct snd_oxfw *oxfw,
goto end;
}
/* OXFW starts to transmit packets with non-zero dbc. */
/*
* OXFW starts to transmit packets with non-zero dbc.
* OXFW postpone transferring packets till handling any asynchronous
* packets. As a result, next isochronous packet includes more data
* blocks than IEC 61883-6 defines.
*/
if (stream == &oxfw->tx_stream)
oxfw->tx_stream.flags |= CIP_SKIP_INIT_DBC_CHECK;
oxfw->tx_stream.flags |= CIP_SKIP_INIT_DBC_CHECK |
CIP_JUMBO_PAYLOAD;
end:
return err;
}