From: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
[ 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 <phil@xxxxxxxxxxxxxxx>
Fixes: 26751de25d25 ("spi: bcm2835: Micro-optimise FIFO loops")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
[1] https://github.com/raspberrypi/linux/issues/4100
Link: https://lore.kernel.org/r/20210211180820.25757-1-nsaenzjulienne@xxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 7694e1ae5b0b2..4257a2d368f71 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:
--
2.27.0
