On Tue, Feb 15, 2022 at 4:58 PM Rob Herring <robh@xxxxxxxxxx> wrote:
>
> On Mon, 14 Feb 2022 16:32:08 +0100, Mårten Lindahl wrote:
> > 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
> >
> > Don't get a new dma_range_map if there already is one. Check for an
> > existing map and reuse it, or else get the map as before. This will
> > prevent overwriting the old map which is still valid.
> >
> > Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx>
> > ---
> >
> > v2:
> > - Reuse range map instead of getting a new and freeing the old.
> >
> > drivers/of/device.c | 9 +++++++--
> > 1 file changed, 7 insertions(+), 2 deletions(-)
> >
>
> Applied, thanks!
Ummm, a bit too quick here. I was looking at the history to add a
Fixes tag. Looking at commit 89c7cb1608ac ("of/device: Update
dma_range_map only when dev has valid dma-ranges"), I think this
change may cause a change in behavior as 'ret' is used as a 'we have a
valid dma-ranges' flag. So if dma_range_map was set, but not from
dma-ranges, the behavior will be different.
Instead, I think this needs to be something like the following patch.
Really we have 3 occurrences of the same clean-up in dd.c and that
should be refactored. But the below is probably better for a backport
and refactoring should come after.
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 9eaaff2f556c..f0a508fd7913 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -629,6 +632,9 @@ static int really_probe(struct device *dev, struct
device_driver *drv)
drv->remove(dev);
devres_release_all(dev);
+ arch_teardown_dma_ops(dev);
+ kfree(dev->dma_range_map);
+ dev->dma_range_map = NULL;
driver_sysfs_remove(dev);
dev->driver = NULL;
dev_set_drvdata(dev, NULL);
@@ -1209,6 +1215,8 @@ static void __device_release_driver(struct
device *dev, struct device *parent)
devres_release_all(dev);
arch_teardown_dma_ops(dev);
+ kfree(dev->dma_range_map);
+ dev->dma_range_map = NULL;
dev->driver = NULL;
dev_set_drvdata(dev, NULL);
if (dev->pm_domain && dev->pm_domain->dismiss)
