PCI: Fix pci_host_bridge struct device release/free handling

The PCI code has several paths where the struct pci_host_bridge is freed
directly. This is wrong because it contains a struct device which is
refcounted and should be freed using put_device(). This can result in
use-after-free errors. I think this problem has existed since 2012 with
commit 7b5436635800 ("PCI: add generic device into pci_host_bridge
struct"). It generally hasn't mattered as most host bridge drivers are
still built-in and can't unbind.

The problem is a struct device should never be freed directly once
device_initialize() is called and a ref is held, but that doesn't happen
until pci_register_host_bridge(). There's then a window between allocating
the host bridge and pci_register_host_bridge() where kfree should be used.
This is fragile and requires callers to do the right thing. To fix this, we
need to split device_register() into device_initialize() and device_add()
calls, so that the host bridge struct is always freed by using a
put_device().

devm_pci_alloc_host_bridge() is using devm_kzalloc() to allocate struct
pci_host_bridge which will be freed directly. Instead, we can use a custom
devres action to call put_device().

Link: https://lore.kernel.org/r/20200513223859.11295-2-robh@kernel.org
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index e21dc71b1907634c4ad5687f6e9180c511ffa609..e064ded6fbec077941068106034c7d1e90fe4631 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -565,7 +565,7 @@ static struct pci_bus *pci_alloc_bus(struct pci_bus *parent)
        return b;
 }
 
-static void devm_pci_release_host_bridge_dev(struct device *dev)
+static void pci_release_host_bridge_dev(struct device *dev)
 {
        struct pci_host_bridge *bridge = to_pci_host_bridge(dev);
 
@@ -574,12 +574,7 @@ static void devm_pci_release_host_bridge_dev(struct device *dev)
 
        pci_free_resource_list(&bridge->windows);
        pci_free_resource_list(&bridge->dma_ranges);
-}
-
-static void pci_release_host_bridge_dev(struct device *dev)
-{
-       devm_pci_release_host_bridge_dev(dev);
-       kfree(to_pci_host_bridge(dev));
+       kfree(bridge);
 }
 
 static void pci_init_host_bridge(struct pci_host_bridge *bridge)
@@ -599,6 +594,8 @@ static void pci_init_host_bridge(struct pci_host_bridge *bridge)
        bridge->native_pme = 1;
        bridge->native_ltr = 1;
        bridge->native_dpc = 1;
+
+       device_initialize(&bridge->dev);
 }
 
 struct pci_host_bridge *pci_alloc_host_bridge(size_t priv)
@@ -616,17 +613,25 @@ struct pci_host_bridge *pci_alloc_host_bridge(size_t priv)
 }
 EXPORT_SYMBOL(pci_alloc_host_bridge);
 
+static void devm_pci_alloc_host_bridge_release(void *data)
+{
+       pci_free_host_bridge(data);
+}
+
 struct pci_host_bridge *devm_pci_alloc_host_bridge(struct device *dev,
                                                   size_t priv)
 {
+       int ret;
        struct pci_host_bridge *bridge;
 
-       bridge = devm_kzalloc(dev, sizeof(*bridge) + priv, GFP_KERNEL);
+       bridge = pci_alloc_host_bridge(priv);
        if (!bridge)
                return NULL;
 
-       pci_init_host_bridge(bridge);
-       bridge->dev.release = devm_pci_release_host_bridge_dev;
+       ret = devm_add_action_or_reset(dev, devm_pci_alloc_host_bridge_release,
+                                      bridge);
+       if (ret)
+               return NULL;
 
        return bridge;
 }
@@ -634,10 +639,7 @@ EXPORT_SYMBOL(devm_pci_alloc_host_bridge);
 
 void pci_free_host_bridge(struct pci_host_bridge *bridge)
 {
-       pci_free_resource_list(&bridge->windows);
-       pci_free_resource_list(&bridge->dma_ranges);
-
-       kfree(bridge);
+       put_device(&bridge->dev);
 }
 EXPORT_SYMBOL(pci_free_host_bridge);
 
@@ -908,7 +910,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
        if (err)
                goto free;
 
-       err = device_register(&bridge->dev);
+       err = device_add(&bridge->dev);
        if (err) {
                put_device(&bridge->dev);
                goto free;
@@ -978,7 +980,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
 
 unregister:
        put_device(&bridge->dev);
-       device_unregister(&bridge->dev);
+       device_del(&bridge->dev);
 
 free:
        kfree(bus);
@@ -2953,7 +2955,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
        return bridge->bus;
 
 err_out:
-       kfree(bridge);
+       put_device(&bridge->dev);
        return NULL;
 }
 EXPORT_SYMBOL_GPL(pci_create_root_bus);

diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index e9c6b120cf451331dc294f50a3ac1315cd37c2c3..95dec03d9f2a990db01998de7e06f6257e26517b 100644 (file)
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -160,6 +160,6 @@ void pci_remove_root_bus(struct pci_bus *bus)
        host_bridge->bus = NULL;
 
        /* remove the host bridge */
-       device_unregister(&host_bridge->dev);
+       device_del(&host_bridge->dev);
 }
 EXPORT_SYMBOL_GPL(pci_remove_root_bus);