[PATCH v2 01/10] spi: Check presence the of ->transfer[_xxx]() before registering a controller

Boris Brezillon
2018-04-10T22:44:59Z

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@bootlin.com>
---
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)
--
2.14.1