| Message ID | 20200513223859.11295-2-robh@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] PCI: Fix pci_register_host_bridge() device_register() error handling | expand |
On Thu, 14 May 2020 at 00:39, Rob Herring <robh@kernel.org> wrote: > > 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(). > > Reported-by: Anders Roxell <anders.roxell@linaro.org> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Signed-off-by: Rob Herring <robh@kernel.org> Thank you Rob for fixing this so quickly! I applied both patches and I couldn't see the use-after-free anymore. Tested-by: Anders Roxell <anders.roxell@linaro.org> Cheers, Anders > --- > drivers/pci/probe.c | 36 +++++++++++++++++++----------------- > drivers/pci/remove.c | 2 +- > 2 files changed, 20 insertions(+), 18 deletions(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index e21dc71b1907..e064ded6fbec 100644 > --- 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 e9c6b120cf45..95dec03d9f2a 100644 > --- 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); > -- > 2.20.1 >
On Wed, May 13, 2020 at 05:38:59PM -0500, Rob Herring wrote: > 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(). > > Reported-by: Anders Roxell <anders.roxell@linaro.org> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Signed-off-by: Rob Herring <robh@kernel.org> > --- > drivers/pci/probe.c | 36 +++++++++++++++++++----------------- > drivers/pci/remove.c | 2 +- > 2 files changed, 20 insertions(+), 18 deletions(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index e21dc71b1907..e064ded6fbec 100644 > --- 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); I think we need to execute device_del() first, then put_device(). Thank you for fixing this code path. Lorenzo > 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 e9c6b120cf45..95dec03d9f2a 100644 > --- 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); > -- > 2.20.1 >
On Thu, May 14, 2020 at 5:30 AM Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > > On Wed, May 13, 2020 at 05:38:59PM -0500, Rob Herring wrote: > > 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(). > > > > Reported-by: Anders Roxell <anders.roxell@linaro.org> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Bjorn Helgaas <bhelgaas@google.com> > > Signed-off-by: Rob Herring <robh@kernel.org> > > --- > > drivers/pci/probe.c | 36 +++++++++++++++++++----------------- > > drivers/pci/remove.c | 2 +- > > 2 files changed, 20 insertions(+), 18 deletions(-) [...] > > @@ -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); > > I think we need to execute device_del() first, then put_device(). No, because after the device_add, there's a get_device() adding the bridge ptr to the bus. So the put_device here is for that. The final put_device() is in the bridge free or devm action. Rob
On Wed, May 13, 2020 at 05:38:59PM -0500, Rob Herring wrote: > 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(). > > Reported-by: Anders Roxell <anders.roxell@linaro.org> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Signed-off-by: Rob Herring <robh@kernel.org> > --- > drivers/pci/probe.c | 36 +++++++++++++++++++----------------- > drivers/pci/remove.c | 2 +- > 2 files changed, 20 insertions(+), 18 deletions(-) Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index e21dc71b1907..e064ded6fbec 100644 > --- 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 e9c6b120cf45..95dec03d9f2a 100644 > --- 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); > -- > 2.20.1 >
On Thu, May 14, 2020 at 12:39 AM Rob Herring <robh@kernel.org> wrote: > > 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(). > > Reported-by: Anders Roxell <anders.roxell@linaro.org> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Signed-off-by: Rob Herring <robh@kernel.org> Thanks for working your way through that bit of code and fixing my mistakes! Your description makes a lot of sense and the code looks reasonable, but I don't understand my own work enough any more to be sure I didn't miss anything. Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index e21dc71b1907..e064ded6fbec 100644 --- 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 e9c6b120cf45..95dec03d9f2a 100644 --- 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);
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(). Reported-by: Anders Roxell <anders.roxell@linaro.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Rob Herring <robh@kernel.org> --- drivers/pci/probe.c | 36 +++++++++++++++++++----------------- drivers/pci/remove.c | 2 +- 2 files changed, 20 insertions(+), 18 deletions(-)