This is a note to let you know that I've just added the patch titled
spi: Skip zero-length transfers in spi_transfer_one_message()
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
spi-skip-zero-length-transfers-in-spi_transfer_one_m.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 09a79c83558ecbbc524439d70de3d7fe668f17b2
Author: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Date: Thu Feb 11 19:08:20 2021 +0100
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 <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>
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 720ab34784c1d..ccca3a7409fac 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -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:
