Unverified Commit b3063203 authored by Nicolas Saenz Julienne's avatar Nicolas Saenz Julienne Committed by Mark Brown
Browse files

spi: Skip zero-length transfers in spi_transfer_one_message() 



With the introduction of 26751de2 ("spi: bcm2835: Micro-optimise
FIFO loops") it has become apparent that some users might initiate
zero-length SPI transfers. A fact the micro-optimization omitted, and
which turned out to cause crashes[1].

Instead of changing the micro-optimization itself, use a bigger hammer
and skip zero-length transfers altogether for drivers using the default
transfer_one_message() implementation.

Reported-by: default avatarPhil Elwell <phil@raspberrypi.com>
Fixes: 26751de2 ("spi: bcm2835: Micro-optimise FIFO loops")
Signed-off-by: default avatarNicolas Saenz Julienne <nsaenzjulienne@suse.de>

[1] https://github.com/raspberrypi/linux/issues/4100
Link: https://lore.kernel.org/r/20210211180820.25757-1-nsaenzjulienne@suse.de



Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 386f771a

drivers/spi/spi.c

+1 −1
Original line number Diff line number Diff line
@@ -1267,7 +1267,7 @@ static int spi_transfer_one_message(struct spi_controller *ctlr, 
			ptp_read_system_prets(xfer->ptp_sts);

		}



		if (xfer->tx_buf || xfer->rx_buf) {

		if ((xfer->tx_buf || xfer->rx_buf) && xfer->len) {

			reinit_completion(&ctlr->xfer_completion);



fallback_pio: