linux-kernel - Re: [PATCH] misc: microchip: pci1xxxx: Fix possible double free in error handling path

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Message-ID: <955f3abf-81b8-4471-82eb-b969dc5d7c9e@wanadoo.fr>
Date: Mon, 6 Jan 2025 22:34:12 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Ma Ke <make24@...as.ac.cn>, kumaravel.thiagarajan@...rochip.com,
 arnd@...db.de, gregkh@...uxfoundation.org
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH] misc: microchip: pci1xxxx: Fix possible double free in
 error handling path

Le 06/01/2025 à 08:40, Ma Ke a écrit :
> When auxiliary_device_add() returns error and then calls
> auxiliary_device_uninit(), the callback function
> gp_auxiliary_device_release() calls kfree() to free memory. Do not
> call kfree() again in the error handling path.
> 
> Fix this by skipping the redundant kfree().
> 
> Found by code review.
> 
> Cc: stable@...r.kernel.org
> Fixes: 393fc2f5948f ("misc: microchip: pci1xxxx: load auxiliary bus driver for the PIO function in the multi-function endpoint of pci1xxxx device.")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---
>   drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c b/drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c
> index 32af2b14ff34..fbd712938bdc 100644
> --- a/drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c
> +++ b/drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c
> @@ -111,6 +111,7 @@ static int gp_aux_bus_probe(struct pci_dev *pdev, const struct pci_device_id *id
>   
>   err_aux_dev_add_1:
>   	auxiliary_device_uninit(&aux_bus->aux_device_wrapper[1]->aux_dev);
> +	goto err_aux_dev_add_0;
>   
>   err_aux_dev_init_1:
>   	ida_free(&gp_client_ida, aux_bus->aux_device_wrapper[1]->aux_dev.id);
> @@ -120,6 +121,7 @@ static int gp_aux_bus_probe(struct pci_dev *pdev, const struct pci_device_id *id
>   
>   err_aux_dev_add_0:
>   	auxiliary_device_uninit(&aux_bus->aux_device_wrapper[0]->aux_dev);
> +	goto err_ret;
>   
>   err_aux_dev_init_0:
>   	ida_free(&gp_client_ida, aux_bus->aux_device_wrapper[0]->aux_dev.id);

Hi,

This is strange because the nearly same patch is in -next since June 
2024 ([1])

It is also in Linux since at least 6.10 ([2])

In [1] and [2], there is also a new err_ret label, which is not part of 
your patch.

On which tree are you working?
Is your patch compile tested?

CJ


[1]: 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c?id=086c6cbcc563c81d55257f9b27e14faf1d0963d3

[2]: 
https://elixir.bootlin.com/linux/v6.10/source/drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gp.c#L116