linux-kernel - Re: [PATCH] misc: ocxl: fix possible double free in ocxl_file_register

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Message-ID: <e18a4b58-4551-aa68-ed52-baeeeaab56bb@linux.ibm.com>
Date:   Tue, 19 Apr 2022 11:09:43 +0200
From:   Frederic Barrat <fbarrat@...ux.ibm.com>
To:     Hangyu Hua <hbh25y@...il.com>, ajd@...ux.ibm.com, arnd@...db.de,
        gregkh@...uxfoundation.org, mpe@...erman.id.au,
        alastair@...ilva.org
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] misc: ocxl: fix possible double free in
 ocxl_file_register_afu



On 18/04/2022 10:57, Hangyu Hua wrote:
> info_release() will be called in device_unregister() when info->dev's
> reference count is 0. So there is no need to call ocxl_afu_put() and
> kfree() again.
> 
> Fix this by adding free_minor() and return to err_unregister error path.
> 
> Fixes: 75ca758adbaf ("ocxl: Create a clear delineation between ocxl backend & frontend")
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---


Thanks for fixing that error path!
I'm now thinking it would be cleaner to have the call to free_minor() in 
the info_release() callback but that would be another patch.
In any case:
Acked-by: Frederic Barrat <fbarrat@...ux.ibm.com>

   Fred


>   drivers/misc/ocxl/file.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/misc/ocxl/file.c b/drivers/misc/ocxl/file.c
> index d881f5e40ad9..6777c419a8da 100644
> --- a/drivers/misc/ocxl/file.c
> +++ b/drivers/misc/ocxl/file.c
> @@ -556,7 +556,9 @@ int ocxl_file_register_afu(struct ocxl_afu *afu)
>   
>   err_unregister:
>   	ocxl_sysfs_unregister_afu(info); // safe to call even if register failed
> +	free_minor(info);
>   	device_unregister(&info->dev);
> +	return rc;
>   err_put:
>   	ocxl_afu_put(afu);
>   	free_minor(info);