RE: [PATCH] HV: hv_balloon: fix memory leak with using debugfs_lookup()

[Michael Kelley (LINUX)]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu@xxxxxxxxxx>
> Cc: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Cc: linux-hyperv@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>