From: Oleg Nesterov <oleg@redhat.com>
To: Rik van Riel <riel@redhat.com>
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
peterz@infradead.org, paulmck@linux.vnet.ibm.com
Subject: Re: [PATCH] fix sighand use after free
Date: Wed, 13 Aug 2014 17:58:02 +0200 [thread overview]
Message-ID: <20140813155802.GA2695@redhat.com> (raw)
In-Reply-To: <20140813115000.73da6136@cuia.bos.redhat.com>
On 08/13, Rik van Riel wrote:
>
> Subject: fix sighand use after free
>
> __lock_task_sighand carefully takes the rcu_read_lock, gets
> tsk->sighand with rcu_dereference, and verifies that the task
> is still using the sighand_struct after taking the spinlock.
>
> This works much better if the sighand struct is actually rcu
> freed.
I promise, I'll send the doc patch soon ;)
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1017,7 +1017,7 @@ void __cleanup_sighand(struct sighand_struct *sighand)
> {
> if (atomic_dec_and_test(&sighand->count)) {
> signalfd_cleanup(sighand);
> - kmem_cache_free(sighand_cachep, sighand);
> + rcu_free(sighand_cachep, sighand);
Please note that sighand_cachep is SLAB_DESTROY_BY_RCU.
Hmm. and what is rcu_free() ?
Oleg.
next prev parent reply other threads:[~2014-08-13 16:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-13 15:50 [PATCH] fix sighand use after free Rik van Riel
2014-08-13 15:58 ` Oleg Nesterov [this message]
2014-08-13 16:09 ` Rik van Riel
2014-08-13 16:19 ` Oleg Nesterov
2014-08-13 16:43 ` Rik van Riel
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