On Sun, 2018-07-01 at 18:02 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx> > > commit ce99319a182fe766be67f96338386f3ec73e321c upstream. > > 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@xxxxxxxxxxx> > Signed-off-by: Mark Brown <broonie@xxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > --- > drivers/spi/spi.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -707,8 +707,14 @@ static int spi_map_buf(struct spi_master > for (i = 0; i < sgs; i++) { > > if (vmalloced_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))); > vm_page = vmalloc_to_page(buf); > if (!vm_page) { > sg_free_table(sgt); I think this makes sense upstream, but in 4.4 it seems to be a no-op since desc_len is always set to PAGE_SIZE when vmalloced_buf is true. This fix depends on (at least) commit df88e91bbfd1 "spi: respect the maximum segment size of DMA device" which went into 4.6. Ben. -- Ben Hutchings, Software Developer Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom