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

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Message-ID: <540DBC36.3020107@oracle.com>
Date:	Mon, 08 Sep 2014 10:24:54 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	john@...nmccutchan.com, rlove@...ve.org, eparis@...isplace.org
CC:	linux-kernel@...r.kernel.org, Al Viro <viro@...IV.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] fsnotify: don't put user context if it was never assigned

Ping?

On 09/03/2014 05:31 PM, Sasha Levin wrote:
> 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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