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spi: Skip zero-length transfers in spi_transfer_one_message()

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With the introduction of 26751de25d ("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@raspberrypi.com>
Fixes: 26751de25d ("spi: bcm2835: Micro-optimise FIFO loops")
Signed-off-by: Nicolas 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: Mark Brown <broonie@kernel.org>
This commit is contained in:
Nicolas Saenz Julienne 2021-02-11 19:08:20 +01:00 committed by Mark Brown
parent 386f771aad
commit b306320322
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1 changed files with 1 additions and 1 deletions
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drivers/spi/spi.c
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@ -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: