linux-kernel - Re: [PATCH 1/1] tty: release_one

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Message-ID: <20100402184823.GB32229@redhat.com>
Date:	Fri, 2 Apr 2010 20:48:23 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...ux.intel.com>, Greg KH <greg@...ah.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serue@...ibm.com>,
	Sukadev Bhattiprolu <sukadev@...ibm.com>, stable@...nel.org
Subject: Re: [PATCH 1/1] tty: release_one_tty() forgets to put pids

On 04/02, Eric W. Biederman wrote:
>
> My general paranoia would suggest setting the pids to NULL.  So that
> we don't have the chance of a use after free.

In this case, I don't think this is needed. We are doing
free_tty_struct()->kfree(tty) right after put_pid()s, nobody
can use these pointers or we have another bug.


Most probably this patch is correct (but perhaps it is not the best fix).
Every time tty does put_pid() it should also clear the pointer. But I am
not sure I grepped enough.

Oleg.

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