linux-kernel - Re: [PATCH] sysfs: check if one entry has been removed before freeing

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Date:	Wed, 3 Apr 2013 11:52:39 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Dave Jones <davej@...hat.com>, Ming Lei <ming.lei@...onical.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, Sasha Levin <levinsasha928@...il.com>
Subject: Re: [PATCH] sysfs: check if one entry has been removed before freeing

On Wed, Apr 3, 2013 at 11:04 AM, Dave Jones <davej@...hat.com> wrote:
> On Wed, Apr 03, 2013 at 10:58:23AM +0800, Ming Lei wrote:
>
>  > diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
>  > index 1bf016b..328ef9b 100644
>  > --- a/fs/sysfs/dir.c
>  > +++ b/fs/sysfs/dir.c
>  > @@ -268,6 +268,13 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
>  >       */
>  >      parent_sd = sd->s_parent;
>  >
>  > +    if (unlikely(!(sd->s_flags & SYSFS_FLAG_REMOVED))) {
>  > +            printk(KERN_ERR "sysfs: free using entry: %s/%s\n",
>  > +                    parent_sd ? parent_sd->s_name : "",
>  > +                    sd->s_name);
>  > +            BUG();
>  > +    }
>
> Please use WARN instead of BUG.  For an in-ram filesystem like
> sysfs, there's no real reason to lock-up the machine in this way
> making it harder to debug.

If WARN is used, the freed memory will be allocated to other
kernel components, then sysfs may change the memory and cause
destruction, so maybe it is better to use BUG to stop kernel.

Thanks,
--
Ming Lei
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