linux-kernel - RE: [PATCH] HV: hv_balloon: fix memory leak with using debugfs

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Message-ID: <BYAPR21MB168826E0AF83D40DE0C704F9D7D79@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Fri, 3 Feb 2023 03:56:06 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] HV: hv_balloon: fix memory leak with using
 debugfs_lookup()

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Sent: Thursday, February 2, 2023 6:09 AM

> 
> When calling debugfs_lookup() the result must have dput() called on it,
> otherwise the memory will leak over time.  To make things simpler, just
> call debugfs_lookup_and_remove() instead which handles all of the logic
> at once.
> 
> Cc: "K. Y. Srinivasan" <kys@...rosoft.com>
> Cc: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: Wei Liu <wei.liu@...nel.org>
> Cc: Dexuan Cui <decui@...rosoft.com>
> Cc: linux-hyperv@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Add a Fixes: tag?  This hv_balloon debugfs code was added in v6.0,
And I see that debugfs_lookup_and_remove() was also added in v6.0.

Fixes: d180e0a1be6c ("Drivers: hv: Create debugfs file with hyper-v balloon usage information")

> ---
>  drivers/hv/hv_balloon.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> index cbe43e2567a7..64ac5bdee3a6 100644
> --- a/drivers/hv/hv_balloon.c
> +++ b/drivers/hv/hv_balloon.c
> @@ -1963,7 +1963,7 @@ static void  hv_balloon_debugfs_init(struct hv_dynmem_device *b)
> 
>  static void  hv_balloon_debugfs_exit(struct hv_dynmem_device *b)
>  {
> -	debugfs_remove(debugfs_lookup("hv-balloon", NULL));
> +	debugfs_lookup_and_remove("hv-balloon", NULL);
>  }
> 
>  #else

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>