From 86f5b0936975e7b6ac37e0f8073e954595fcc688 Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Thu, 11 Feb 2021 19:08:20 +0100 Subject: [PATCH] spi: Skip zero-length transfers in spi_transfer_one_message() [ Upstream commit b306320322c9cfaa465bc2c7367acf6072b1ac0e ] With the introduction of 26751de25d25 ("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: Phil Elwell Fixes: 26751de25d25 ("spi: bcm2835: Micro-optimise FIFO loops") Signed-off-by: Nicolas Saenz Julienne [1] https://github.com/raspberrypi/linux/issues/4100 Link: https://lore.kernel.org/r/20210211180820.25757-1-nsaenzjulienne@suse.de Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- drivers/spi/spi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 7694e1ae5b0b..4257a2d368f7 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -1259,7 +1259,7 @@ 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: