[PATCH v3] memory: fsl_ifc: Clear global controller pointer on probe failure and remove

[Reid Downing <skibletz@gmail.com>]

fsl_ifc_ctrl_dev is assigned early in fsl_ifc_ctrl_probe() to a
devm-allocated structure. If probe fails afterwards, or when the device
is removed, that memory is freed and the registers are unmapped, but the
global still points at it. fsl_ifc_find() and fsl_ifc_nand_probe() only
check it for NULL, so a later call can dereference freed memory or an
unmapped register region.

Clear the pointer on the probe error paths and in remove, once the IRQs
have been released. The global cannot be published later in probe
instead, because ifc_in32()/ifc_out32() and the NAND child probed from
of_platform_default_populate() depend on it.

Signed-off-by: Reid Downing <skibletz@gmail.com>
---
Changes in v3:
 - Use my real name in Author and Signed-off-by (earlier versions had a
   handle appended).
 - Generate the patch with git against drivers/memory/fsl_ifc.c; the
   earlier versions used a path that could not be applied. Sorry for the
   noise, and for sending two unversioned copies. Those were v1 and v2,
   and this v3 supersedes them.
 - Change of approach: v1 and v2 delayed publishing fsl_ifc_ctrl_dev until
   the end of probe, but ifc_in32()/ifc_out32() and fsl_ifc_nand_probe()
   use the global during probe, so that would break the driver. v3 keeps
   the early assignment and instead clears the pointer on probe failure
   and in remove.
 - Dropped the nand_irq guard from the earlier versions; it was unrelated
   to this fix.

Not compile-tested (no PowerPC build setup); the change is four
assignments of NULL.

 drivers/memory/fsl_ifc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/memory/fsl_ifc.c b/drivers/memory/fsl_ifc.c
index e89e0c6cc..abacd90d6 100644
--- a/drivers/memory/fsl_ifc.c
+++ b/drivers/memory/fsl_ifc.c
@@ -95,6 +95,8 @@ static void fsl_ifc_ctrl_remove(struct platform_device *dev)
 	irq_dispose_mapping(ctrl->nand_irq);
 	irq_dispose_mapping(ctrl->irq);
 
+	/* Children and IRQs are gone; stop lookups before unmapping. */
+	fsl_ifc_ctrl_dev = NULL;
 	iounmap(ctrl->gregs);
 
 	dev_set_drvdata(&dev->dev, NULL);
@@ -218,6 +220,7 @@ static int fsl_ifc_ctrl_probe(struct platform_device *dev)
 	fsl_ifc_ctrl_dev->gregs = of_iomap(dev->dev.of_node, 0);
 	if (!fsl_ifc_ctrl_dev->gregs) {
 		dev_err(&dev->dev, "failed to get memory region\n");
+		fsl_ifc_ctrl_dev = NULL;
 		return -ENODEV;
 	}
 
@@ -300,6 +303,7 @@ static int fsl_ifc_ctrl_probe(struct platform_device *dev)
 	irq_dispose_mapping(fsl_ifc_ctrl_dev->irq);
 err:
 	iounmap(fsl_ifc_ctrl_dev->gregs);
+	fsl_ifc_ctrl_dev = NULL;
 	return ret;
 }
 
-- 
2.53.0