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usb: dwc2: Fix out-of-bounds access, fix chunk size 

Fix two errors in transfer len calculation, move loop invariant code out
of loop.

If xfer_len is equal to CONFIG_DWC2_MAX_TRANSFER_SIZE (or slightly
smaller), the xfer_len will be to large, e.g.:
  xfer_len = MAX_TRANSFER_SIZE = 65535
  max packet size = 512
    => num_packets = 128
    => IN xfer_len = 65536

For OUT transactions larger than (65536 - mps) bytes, the xfer_len
determination is quite awkward, it is only correct due to:
- max_packet_size for control/bulk/interrupt is required to be
  power-of-two.
- (CONFIG_DWC2_MAX_TRANSFER_SIZE + 1) % max-packet-size is zero
  for all allowed (2^3 ... 2^9) packet sizes

As the max xfer len is loop invariant, it can be moved out of the loop.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
This commit is contained in:
Stefan Brüns 2016-01-17 04:09:51 +01:00 committed by Marek Vasut
parent 12f229ea8f
commit 56a7bbd741
1 changed files with 15 additions and 15 deletions
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30
drivers/usb/host/dwc2.c
View File

@ -786,34 +786,34 @@ int chunk_msg(struct dwc2_priv *priv, struct usb_device *dev,
uint32_t xfer_len;
uint32_t num_packets;
int stop_transfer = 0;
uint32_t max_xfer_len;
debug("%s: msg: pipe %lx pid %d in %d len %d\n", __func__, pipe, *pid,
in, len);
max_xfer_len = CONFIG_DWC2_MAX_PACKET_COUNT * max;
if (max_xfer_len > CONFIG_DWC2_MAX_TRANSFER_SIZE)
max_xfer_len = CONFIG_DWC2_MAX_TRANSFER_SIZE;
if (max_xfer_len > DWC2_DATA_BUF_SIZE)
max_xfer_len = DWC2_DATA_BUF_SIZE;
/* Make sure that max_xfer_len is a multiple of max packet size. */
num_packets = max_xfer_len / max;
max_xfer_len = num_packets * max;
do {
/* Initialize channel */
dwc_otg_hc_init(regs, DWC2_HC_CHANNEL, dev, devnum, ep, in,
eptype, max);
xfer_len = len - done;
if (xfer_len > CONFIG_DWC2_MAX_TRANSFER_SIZE)
xfer_len = CONFIG_DWC2_MAX_TRANSFER_SIZE - max + 1;
if (xfer_len > DWC2_DATA_BUF_SIZE)
xfer_len = DWC2_DATA_BUF_SIZE - max + 1;
/* Make sure that xfer_len is a multiple of max packet size. */
if (xfer_len > 0) {
if (xfer_len > max_xfer_len)
xfer_len = max_xfer_len;
else if (xfer_len > max)
num_packets = (xfer_len + max - 1) / max;
if (num_packets > CONFIG_DWC2_MAX_PACKET_COUNT) {
num_packets = CONFIG_DWC2_MAX_PACKET_COUNT;
xfer_len = num_packets * max;
}
} else {
else
num_packets = 1;
}
if (in)
xfer_len = num_packets * max;
debug("%s: chunk: pid %d xfer_len %u pkts %u\n", __func__,
*pid, xfer_len, num_packets);