The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From ce99319a182fe766be67f96338386f3ec73e321c Mon Sep 17 00:00:00 2001
From: Maxime Chevallier maxime.chevallier@bootlin.com Date: Fri, 2 Mar 2018 15:55:09 +0100 Subject: [PATCH] spi: Fix scatterlist elements size in spi_map_buf
When SPI transfers can be offloaded using DMA, the SPI core need to build a scatterlist to make sure that the buffer to be transferred is dma-able.
This patch fixes the scatterlist entry size computation in the case where the maximum acceptable scatterlist entry supported by the DMA controller is less than PAGE_SIZE, when the buffer is vmalloced.
For each entry, the actual size is given by the minimum between the desc_len (which is the max buffer size supported by the DMA controller) and the remaining buffer length until we cross a page boundary.
Fixes: 65598c13fd66 ("spi: Fix per-page mapping of unaligned vmalloc-ed buffer") Signed-off-by: Maxime Chevallier maxime.chevallier@bootlin.com Signed-off-by: Mark Brown broonie@kernel.org Cc: stable@vger.kernel.org
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index b33a727a0158..4153f959f28c 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -779,8 +779,14 @@ static int spi_map_buf(struct spi_controller *ctlr, struct device *dev, for (i = 0; i < sgs; i++) {
if (vmalloced_buf || kmap_buf) { - min = min_t(size_t, - len, desc_len - offset_in_page(buf)); + /* + * Next scatterlist entry size is the minimum between + * the desc_len and the remaining buffer length that + * fits in a page. + */ + min = min_t(size_t, desc_len, + min_t(size_t, len, + PAGE_SIZE - offset_in_page(buf))); if (vmalloced_buf) vm_page = vmalloc_to_page(buf); else