Commit cc211863 authored Mar 07, 2019 by Chris Lesiak Committed by Greg Kroah-Hartman May 31, 2019

spi: Fix zero length xfer bug



[ Upstream commit 5442dcaa0d90fc376bdfc179a018931a8f43dea4 ]

This fixes a bug for messages containing both zero length and
unidirectional xfers.

The function spi_map_msg will allocate dummy tx and/or rx buffers
for use with unidirectional transfers when the hardware can only do
a bidirectional transfer.  That dummy buffer will be used in place
of a NULL buffer even when the xfer length is 0.

Then in the function __spi_map_msg, if he hardware can dma,
the zero length xfer will have spi_map_buf called on the dummy
buffer.

Eventually, __sg_alloc_table is called and returns -EINVAL
because nents == 0.

This fix prevents the error by not using the dummy buffer when
the xfer length is zero.

Signed-off-by: Chris Lesiak <chris.lesiak@licor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 8f7f333a

drivers/spi/spi.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -982,6 +982,8 @@ static int spi_map_msg(struct spi_controller ctlr, struct spi_message msg)
		if (max_tx \|\| max_rx) {
		list_for_each_entry(xfer, &msg->transfers,
		transfer_list) {
		if (!xfer->len)
		continue;
		if (!xfer->tx_buf)
		xfer->tx_buf = ctlr->dummy_tx;
		if (!xfer->rx_buf)