Messages in this thread | | | From | Ricardo Ribalda Delgado <> | Date | Mon, 20 Apr 2015 22:24:25 +0200 | Subject | Re: [PATCH] kernel/resource: Invalid memory access in __release_resource |
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Hi Bjorn!
Thanks for your promtly response.
On Mon, Apr 20, 2015 at 9:28 PM, Bjorn Helgaas <bhelgaas@google.com> wrote: > [+cc Grant (author of ac80a51e2ce5)] > > Hi Ricardo, > > On Mon, Apr 20, 2015 at 06:22:52PM +0200, Ricardo Ribalda Delgado wrote: >> >> If of_platform_depopulate is called later, resource->parent is >> accessed (Offset 0x30 of address 0), causing a kernel error. > > Interesting; how'd you find this? It looks like the > of_platform_depopulate() code has been this way for a long time, so we > must be doing something new that makes us trip over this now. More > analysis below...
I have an out of tree driver that dynamically adds devices to the device tree.
It was developed before the dynamic_of and dt_overlays existed. Now I am porting my code to the new interfaces available. I am trying to do it small steps.
First step was being able to depopulate a previously loaded device tree. Old, code was calling of_platform_populate, so calling of_platform_depopulate looked like the right choice. Unfortunately everything crashed, and it turned out that this was the issue.
On my defense I would say, that the plan is to make this driver public, once the hardware is stabilized and sold to the public.
>> @@ -237,6 +237,9 @@ static int __release_resource(struct resource *old) >> { >> struct resource *tmp, **p; >> >> + if (!old->parent) >> + return -EINVAL; > > This path has been fine for a long time without testing for a NULL > pointer, so I suspect this change papers over an issue that would be > better fixed elsewhere. >
This code is pretty tested, but dynamic remove is not.
> From reading drivers/base/platform.c, it looks like the intent is > that platform device users would use these interfaces:
I can take a look to modify OF to use insert_resource(), but I still think that no matter what, we should add this extra check, like the propossed patch or maybe with a BUG_ON()....
Lets see what Grant thinks about this.
Thanks again!
-- Ricardo Ribalda
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