linux-kernel - Re: [PATCH] fsnotify: don't put user context if it was never assigned

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Date:	Wed, 03 Sep 2014 17:31:15 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Sasha Levin <sasha.levin@...cle.com>, john@...nmccutchan.com,
	rlove@...ve.org, eparis@...isplace.org
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fsnotify: don't put user context if it was never assigned

Ping? This is a NULL ptr deref that userspace can trigger.

On 07/29/2014 09:25 AM, Sasha Levin wrote:
> On some failure paths we may attempt to free user context even
> if it wasn't assigned yet. This will cause a NULL ptr deref
> and a kernel BUG.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  fs/notify/inotify/inotify_fsnotify.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
> index 43ab1e1..9c8187e 100644
> --- a/fs/notify/inotify/inotify_fsnotify.c
> +++ b/fs/notify/inotify/inotify_fsnotify.c
> @@ -165,8 +165,10 @@ static void inotify_free_group_priv(struct fsnotify_group *group)
>  	/* ideally the idr is empty and we won't hit the BUG in the callback */
>  	idr_for_each(&group->inotify_data.idr, idr_callback, group);
>  	idr_destroy(&group->inotify_data.idr);
> -	atomic_dec(&group->inotify_data.user->inotify_devs);
> -	free_uid(group->inotify_data.user);
> +	if (group->inotify_data.user) {
> +		atomic_dec(&group->inotify_data.user->inotify_devs);
> +		free_uid(group->inotify_data.user);
> +	}
>  }
>  
>  static void inotify_free_event(struct fsnotify_event *fsn_event)
> 

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