linux-kernel - Re: fix del_timer() misuse for ->s_err

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Message-ID: <20131209015628.GA12883@thunk.org>
Date:	Sun, 8 Dec 2013 20:56:28 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: fix del_timer() misuse for ->s_err_report

On Wed, Dec 04, 2013 at 07:29:26AM +0000, Al Viro wrote:
> That thing should be del_timer_sync(); consider what happens
> if ext4_put_super() call of del_timer() happens to come just as it's
> getting run on another CPU.  Since that timer reschedules itself
> to run next day, you are pretty much guaranteed that you'll end up
> with kfree'd scheduled timer, with usual fun consequences.  AFAICS,
> that's -stable fodder all way back to 2010... [the second del_timer_sync()
> is almost certainly not needed, but it doesn't hurt either]
> 
> Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

Nice catch.  Thanks, applied.

						- Ted
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