Applied "spi: Check presence the of ->transfer[_xxx]() before registering a controller" to the spi tree

[Mark Brown]

The patch

   spi: Check presence the of ->transfer[_xxx]() before registering a controller

has been applied to the spi tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From bd40560ac3365e3a2d512d0ad03ceb6c7f603c0c Mon Sep 17 00:00:00 2001
From: Boris Brezillon <boris.brezillon at bootlin.com>
Date: Wed, 11 Apr 2018 00:44:30 +0200
Subject: [PATCH] spi: Check presence the of ->transfer[_xxx]() before
 registering a controller

Right now, no checks are done on the presence of a ->transfer[_xxx]()
method, which can lead to a NULL pointer dereference when someone
starts sending something on the bus.

Do the check at registration time and refuse to add the controller if
all ->transfer[_xxx]() pointers are NULL.

Signed-off-by: Boris Brezillon <boris.brezillon at bootlin.com>
Signed-off-by: Mark Brown <broonie at kernel.org>
---
 drivers/spi/spi.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 7b213faa0a2b..24369e437c6b 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2063,6 +2063,19 @@ static int of_spi_register_master(struct spi_controller *ctlr)
 }
 #endif
 
+static int spi_controller_check_ops(struct spi_controller *ctlr)
+{
+	/*
+	 * The controller must at least implement one of the ->transfer()
+	 * hooks.
+	 */
+	if (!ctlr->transfer && !ctlr->transfer_one &&
+	    !ctlr->transfer_one_message)
+		return -EINVAL;
+
+	return 0;
+}
+
 /**
  * spi_register_controller - register SPI master or slave controller
  * @ctlr: initialized master, originally from spi_alloc_master() or
@@ -2096,6 +2109,14 @@ int spi_register_controller(struct spi_controller *ctlr)
 	if (!dev)
 		return -ENODEV;
 
+	/*
+	 * Make sure all necessary hooks are implemented before registering
+	 * the SPI controller.
+	 */
+	status = spi_controller_check_ops(ctlr);
+	if (status)
+		return status;
+
 	if (!spi_controller_is_slave(ctlr)) {
 		status = of_spi_register_master(ctlr);
 		if (status)
-- 
2.17.0