[PATCH] PCI: endpoint: Fix a double free in __pci_epc_create()

[PATCH] PCI: endpoint: Fix a double free in __pci_epc_create()

[Ma Ke]

The put_device(&epc->dev) call will trigger pci_epc_release() which
frees "epc" so the kfree(epc) on the next line is a double free.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: 5e8cb4033807 ("PCI: endpoint: Add EP core layer to enable EP controller and EP functions")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 drivers/pci/endpoint/pci-epc-core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 46c9a5c3ca14..652350f054cf 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -818,7 +818,6 @@ __pci_epc_create(struct device *dev, const struct pci_epc_ops *ops,
 
 put_dev:
 	put_device(&epc->dev);
-	kfree(epc);
 
 err_ret:
 	return ERR_PTR(ret);
-- 
2.25.1

Re: [PATCH] PCI: endpoint: Fix a double free in __pci_epc_create()

[Krzysztof Wilczyński]

Hello,

> The put_device(&epc->dev) call will trigger pci_epc_release() which
> frees "epc" so the kfree(epc) on the next line is a double free.
> 
> Found by code review.
> 
> Cc: stable@vger.kernel.org
> Fixes: 5e8cb4033807 ("PCI: endpoint: Add EP core layer to enable EP controller and EP functions")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>

Which kernel release did you review?  I don't see this kfree() when looking
at the current code base per:

  https://elixir.bootlin.com/linux/v6.13-rc1/source/drivers/pci/endpoint/pci-epc-core.c#L956-L1020

	Krzysztof

Re: [PATCH] PCI: endpoint: Fix a double free in __pci_epc_create()

[Krzysztof Wilczyński]

Hello,

> > The put_device(&epc->dev) call will trigger pci_epc_release() which
> > frees "epc" so the kfree(epc) on the next line is a double free.
> > 
> > Found by code review.

[...]
> Which kernel release did you review?  I don't see this kfree() when looking
> at the current code base per:
> 
>   https://elixir.bootlin.com/linux/v6.13-rc1/source/drivers/pci/endpoint/pci-epc-core.c#L956-L1020

I will answer my own question.  This surplus kfree() has already been
removed as part of the following commit:

  c9501d268944 ("PCI: endpoint: Fix double free in __pci_epc_create()")

Nevertheless, thank you for the patch.

	Krzysztof

[PATCH] PCI: endpoint: Fix a double free in __pci_epc_create()

[Ma Ke]

The put_device(&epc->dev) call will trigger pci_epc_release() which
frees "epc" so the kfree(epc) on the next line is a double free.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: 5e8cb4033807 ("PCI: endpoint: Add EP core layer to enable EP controller and EP functions")
Signed-off-by: Ma Ke <make_ruc2021@163.com>
---
 drivers/pci/endpoint/pci-epc-core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 46c9a5c3ca14..652350f054cf 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -818,7 +818,6 @@ __pci_epc_create(struct device *dev, const struct pci_epc_ops *ops,
 
 put_dev:
 	put_device(&epc->dev);
-	kfree(epc);
 
 err_ret:
 	return ERR_PTR(ret);
-- 
2.25.1

Re: [PATCH] PCI: endpoint: Fix a double free in __pci_epc_create()

[Markus Elfring]

> The put_device(&epc->dev) call will trigger pci_epc_release() which
> frees "epc" so the kfree(epc) on the next line is a double free.

See also:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.13-rc5#n94


> Found by code review.

Would you become interested to check how many similar control flows
can still be detected by the means of automated advanced source code analyses?

Regards,
Markus