Messages in this thread | | | Date | Fri, 11 Dec 2020 09:46:52 -0600 | From | Rob Herring <> | Subject | Re: [PATCH] PCI: fix use-after-free in pci_register_host_bridge |
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On Fri, Nov 20, 2020 at 03:48:48PM +0800, Qinglang Miao wrote: > When put_device(&bridge->dev) being called, kfree(bridge) is inside > of release function, so the following device_del would cause a > use-after-free bug. > > Fixes: 37d6a0a6f470 ("PCI: Add pci_register_host_bridge() interface")
That commit did have some problems, but this patch doesn't apply to that commit. See commits 1b54ae8327a4 and 9885440b16b8.
> Reported-by: Hulk Robot <hulkci@huawei.com> > Signed-off-by: Qinglang Miao <miaoqinglang@huawei.com> > --- > drivers/pci/probe.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 4289030b0..82292e87e 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -991,8 +991,8 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) > return 0; > > unregister: > - put_device(&bridge->dev); > device_del(&bridge->dev); > + put_device(&bridge->dev);
I don't think this is right.
Let's look at pci_register_host_bridge() with only the relevant sections:
static int pci_register_host_bridge(struct pci_host_bridge *bridge) { ...
err = device_add(&bridge->dev); if (err) { put_device(&bridge->dev); goto free; } bus->bridge = get_device(&bridge->dev);
... if (err) goto unregister; ...
return 0;
unregister: put_device(&bridge->dev); device_del(&bridge->dev);
free: kfree(bus); return err; }
The documentation for device_add says this: * Rule of thumb is: if device_add() succeeds, you should call * device_del() when you want to get rid of it. If device_add() has * *not* succeeded, use *only* put_device() to drop the reference * count.
The put_device at the end is to balance the get_device after device_add. It will *only* decrement the use count. Then we call device_del as the documentation says.
Rob
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