This is a note to let you know that I've just added the patch titled PCI: Fix pci_host_bridge struct device release/free handling to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pci-fix-pci_host_bridge-struct-device-release-free-handling.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 9885440b16b8fc1dd7275800fd28f56a92f60896 Mon Sep 17 00:00:00 2001 From: Rob Herring <robh@xxxxxxxxxx> Date: Wed, 13 May 2020 17:38:59 -0500 Subject: PCI: Fix pci_host_bridge struct device release/free handling From: Rob Herring <robh@xxxxxxxxxx> commit 9885440b16b8fc1dd7275800fd28f56a92f60896 upstream. 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@xxxxxxxxxx Reported-by: Anders Roxell <anders.roxell@xxxxxxxxxx> Tested-by: Anders Roxell <anders.roxell@xxxxxxxxxx> Signed-off-by: Rob Herring <robh@xxxxxxxxxx> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> Acked-by: Arnd Bergmann <arnd@xxxxxxxx> [tyhicks: Minor contextual change in pci_init_host_bridge() due to the lack of a native_dpc member in the pci_host_bridge struct. It was added in v5.7 with commit ac1c8e35a326 ("PCI/DPC: Add Error Disconnect Recover (EDR) support")] Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/pci/probe.c | 36 +++++++++++++++++++----------------- drivers/pci/remove.c | 2 +- 2 files changed, 20 insertions(+), 18 deletions(-) --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -564,7 +564,7 @@ static struct pci_bus *pci_alloc_bus(str 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); @@ -573,12 +573,7 @@ static void devm_pci_release_host_bridge 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) @@ -597,6 +592,8 @@ static void pci_init_host_bridge(struct bridge->native_shpc_hotplug = 1; bridge->native_pme = 1; bridge->native_ltr = 1; + + device_initialize(&bridge->dev); } struct pci_host_bridge *pci_alloc_host_bridge(size_t priv) @@ -614,17 +611,25 @@ struct pci_host_bridge *pci_alloc_host_b } 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; } @@ -632,10 +637,7 @@ 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); @@ -866,7 +868,7 @@ static int pci_register_host_bridge(stru if (err) goto free; - err = device_register(&bridge->dev); + err = device_add(&bridge->dev); if (err) { put_device(&bridge->dev); goto free; @@ -933,7 +935,7 @@ static int pci_register_host_bridge(stru unregister: put_device(&bridge->dev); - device_unregister(&bridge->dev); + device_del(&bridge->dev); free: kfree(bus); @@ -2945,7 +2947,7 @@ struct pci_bus *pci_create_root_bus(stru return bridge->bus; err_out: - kfree(bridge); + put_device(&bridge->dev); return NULL; } EXPORT_SYMBOL_GPL(pci_create_root_bus); --- a/drivers/pci/remove.c +++ b/drivers/pci/remove.c @@ -160,6 +160,6 @@ void pci_remove_root_bus(struct pci_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); Patches currently in stable-queue which might be from robh@xxxxxxxxxx are queue-5.4/pci-fix-pci_host_bridge-struct-device-release-free-handling.patch