[PATCH 1/2] rapidio/tsi721_dma: fix failure to obtain transaction descriptor

From: Alexandre Bounine
Date: Thu Jul 24 2014 - 16:04:28 EST

This is a bug fix for the situation when function tsi721_desc_get() fails
to obtain a free transaction descriptor.

The bug usually results in a memory access crash dump when data transfer
scatter-gather list has more entries than size of hardware buffer
descriptors ring. This fix ensures that error is properly returned to a caller
instead of an invalid entry.

This patch is applicable to kernel versions starting from v3.5.

Signed-off-by: Alexandre Bounine <alexandre.bounine@xxxxxxx>
Cc: Matt Porter <mporter@xxxxxxxxxxxxxxxxxxx>
Cc: Andre van Herk <andre.van.herk@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Stef van Os <stef.van.os@xxxxxxxxxxxxxxxxxxxxxxxxx>
Cc: Vinod Koul <vinod.koul@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: <linux-kernel@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
drivers/rapidio/devices/tsi721_dma.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/rapidio/devices/tsi721_dma.c b/drivers/rapidio/devices/tsi721_dma.c
index 9b60b1f..44341dc 100644
--- a/drivers/rapidio/devices/tsi721_dma.c
+++ b/drivers/rapidio/devices/tsi721_dma.c
@@ -287,6 +287,12 @@ struct tsi721_tx_desc *tsi721_desc_get(struct tsi721_bdma_chan *bdma_chan)
"desc %p not ACKed\n", tx_desc);

+ if (ret == NULL) {
+ dev_dbg(bdma_chan->dchan.device->dev,
+ "%s: unable to obtain tx descriptor\n", __func__);
+ goto err_out;
+ }
i = bdma_chan->wr_count_next % bdma_chan->bd_num;
if (i == bdma_chan->bd_num - 1) {
i = 0;
@@ -297,7 +303,7 @@ struct tsi721_tx_desc *tsi721_desc_get(struct tsi721_bdma_chan *bdma_chan)
tx_desc->txd.phys = bdma_chan->bd_phys +
i * sizeof(struct tsi721_dma_desc);
tx_desc->hw_desc = &((struct tsi721_dma_desc *)bdma_chan->bd_base)[i];

return ret;

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