[PATCH] of: dma_configure: Free old DMA map range

[Mårten Lindahl <marten.lindahl@xxxxxxxx>]

When unbinding/binding a driver with DMA mapped memory, the DMA map is
not freed when the driver is reloaded. This leads to a memory leak when
the DMA map is overwritten when reprobing the driver.

This can be reproduced with a platform driver having a dma-range:

dummy {
	...
	#address-cells = <0x2>;
	#size-cells = <0x2>;
	ranges;
	dma-ranges = <...>;
	...
};

and then unbinding/binding it:

~# echo soc:dummy >/sys/bus/platform/drivers/<driver>/unbind

DMA map object 0xffffff800b0ae540 still being held by &pdev->dev

~# echo soc:dummy >/sys/bus/platform/drivers/<driver>/bind
~# echo scan > /sys/kernel/debug/kmemleak
~# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffffff800b0ae540 (size 64):
  comm "sh", pid 833, jiffies 4295174550 (age 2535.352s)
  hex dump (first 32 bytes):
    00 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 80 00 00 00 00 00 00 00 80 00 00 00 00  ................
  backtrace:
    [<ffffffefd1694708>] create_object.isra.0+0x108/0x344
    [<ffffffefd1d1a850>] kmemleak_alloc+0x8c/0xd0
    [<ffffffefd167e2d0>] __kmalloc+0x440/0x6f0
    [<ffffffefd1a960a4>] of_dma_get_range+0x124/0x220
    [<ffffffefd1a8ce90>] of_dma_configure_id+0x40/0x2d0
    [<ffffffefd198b68c>] platform_dma_configure+0x5c/0xa4
    [<ffffffefd198846c>] really_probe+0x8c/0x514
    [<ffffffefd1988990>] __driver_probe_device+0x9c/0x19c
    [<ffffffefd1988cd8>] device_driver_attach+0x54/0xbc
    [<ffffffefd1986634>] bind_store+0xc4/0x120
    [<ffffffefd19856e0>] drv_attr_store+0x30/0x44
    [<ffffffefd173c9b0>] sysfs_kf_write+0x50/0x60
    [<ffffffefd173c1c4>] kernfs_fop_write_iter+0x124/0x1b4
    [<ffffffefd16a013c>] new_sync_write+0xdc/0x160
    [<ffffffefd16a256c>] vfs_write+0x23c/0x2a0
    [<ffffffefd16a2758>] ksys_write+0x64/0xec

Prevent overwriting the dma_range_map by freeing it before saving the
new map.

Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx>
---
 drivers/of/device.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 874f031442dc..a67703d09bfd 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -156,6 +156,12 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
 			kfree(map);
 			return -EINVAL;
 		}
+
+		/*
+		 * Since we are about to set a new range map we should make sure we
+		 * do not overwrite any existing one without having freed it first.
+		 */
+		kfree(dev->dma_range_map);
 	}
 
 	/*
-- 
2.30.2