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rapidio/tsi721_dma: fix failure to obtain transaction descriptor
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@idt.com> Cc: Matt Porter <mporter@kernel.crashing.org> Cc: Andre van Herk <andre.van.herk@prodrive-technologies.com> Cc: Stef van Os <stef.van.os@prodrive-technologies.com> Cc: Vinod Koul <vinod.koul@intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: <stable@vger.kernel.org> [3.5+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -287,6 +287,12 @@ struct tsi721_tx_desc *tsi721_desc_get(struct tsi721_bdma_chan *bdma_chan)
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"desc %p not ACKed\n", tx_desc);
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}
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if (ret == NULL) {
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dev_dbg(bdma_chan->dchan.device->dev,
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"%s: unable to obtain tx descriptor\n", __func__);
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goto err_out;
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}
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i = bdma_chan->wr_count_next % bdma_chan->bd_num;
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if (i == bdma_chan->bd_num - 1) {
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i = 0;
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@ -297,7 +303,7 @@ struct tsi721_tx_desc *tsi721_desc_get(struct tsi721_bdma_chan *bdma_chan)
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tx_desc->txd.phys = bdma_chan->bd_phys +
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i * sizeof(struct tsi721_dma_desc);
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tx_desc->hw_desc = &((struct tsi721_dma_desc *)bdma_chan->bd_base)[i];
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err_out:
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spin_unlock_bh(&bdma_chan->lock);
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return ret;
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