linux-kernel - Re: [BUG] fs: inotify_handle_event() reading un-init memory

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Date:	Tue, 16 Jun 2015 15:52:09 +0200
From:	Jan Kara <jack@...e.cz>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	Jan Kara <jack@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] fs: inotify_handle_event() reading un-init memory

On Tue 16-06-15 13:33:18, Jesper Dangaard Brouer wrote:
> Caught by kmemcheck.
> 
> Don't know the fix... just pointed at the bug.
> 
> Introduced in commit 7053aee26a3 ("fsnotify: do not share
> events between notification groups").
> ---
>  fs/notify/inotify/inotify_fsnotify.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
> index 2cd900c2c737..370d66dc4ddb 100644
> --- a/fs/notify/inotify/inotify_fsnotify.c
> +++ b/fs/notify/inotify/inotify_fsnotify.c
> @@ -96,11 +96,12 @@ int inotify_handle_event(struct fsnotify_group *group,
>  	i_mark = container_of(inode_mark, struct inotify_inode_mark,
>  			      fsn_mark);
>  
> +	// new object alloc here
>  	event = kmalloc(alloc_len, GFP_KERNEL);
>  	if (unlikely(!event))
>  		return -ENOMEM;
>  
> -	fsn_event = &event->fse;
> +	fsn_event = &event->fse; // This looks wrong!?! read from un-init mem?

Where is here any read? This is just a pointer arithmetics where we add
offset of 'fse' entry to 'event' address.

								Honza

>  	fsnotify_init_event(fsn_event, inode, mask);
>  	event->wd = i_mark->wd;
>  	event->sync_cookie = cookie;
> 
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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