Date: Fri, 1 Mar 2013 13:35:11 -0800
From: Tejun Heo <tj@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: markus@trippelsdorf.de, linux-kernel@vger.kernel.org
Subject: Re: WARNING: at lib/idr.c:678 idr_find_slowpath+0x97/0xc0()
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 <20130301133159.0711f81a.akpm@linux-foundation.org>
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Hello, Andrew.

On Fri, Mar 01, 2013 at 01:31:59PM -0800, Andrew Morton wrote:
> okluar passed a negative `wd' into inotify_rm_watch()?
> 
> I wonder why it did that.  I doubt if inotify_add_watch() ever returns
> negative descriptors, in which case I expect that okular's call to
> inotify_add_watch() returned -1 and an errno and okular forgot to check
> it, and later passed that -1 back into inotify_rm_watch().
> 
> Anyway, I guess we need to make inotify_add_watch() refuse to return
> negative descriptors (presumably this is already the case due to idr
> internals) and make inotify_rm_watch() trap negative values of `wd' up
> front.
> 
> I wonder how many other such gremlins the IDR checking has added.

The WARN_ON() is just for cases where someone might be doing something
crazy with the previous behavior of ignoring high bit.  Maybe I was
being overly paranoid and we should just drop it from idr_find().

Thanks.

-- 
tejun
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