linux-kernel - Re: [PATCH 1/1][BUG][TAKE2] KEYRINGS: find_keyring_by

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Message-ID: <50d28d42d9f97dd6444c54265de9cd4b.squirrel@webmail-b.css.fujitsu.com>
Date:	Sat, 24 Apr 2010 09:32:54 +0900 (JST)
From:	岡嶋　寿行 
	<toshi.okajima@...fujitsu.com>
To:	"David Howells" <dhowells@...hat.com>
Cc:	"Toshiyuki Okajima" <toshi.okajima@...fujitsu.com>,
	dhowells@...hat.com, keyrings@...ux-nfs.org, security@...nel.org,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1][BUG][TAKE2] KEYRINGS: find_keyring_by_name() can
 gain the freed keyring

> Toshiyuki Okajima <toshi.okajima@...fujitsu.com> wrote:
>
>> > Better still, atomic_inc_not_zero().  How about the attached patch?
>> Your fix looks good to me. But, if usage count of the keyring is 0,
>> I think it better to return -ENOKEY immediately.
>

> The problem with that is that someone else may have created a keyring with
> the
> same name that you can't then reach until the dead keyring is deleted.

OK. I understand.
---
Once find_keyring_by_name() returns -ENOKEY, the new user creates a
new key. So, both the deleting key and the new key may exist.
Therefore at next find_keyring_by_name() call, we should find the new
key and ignore the deleting key.
---

Toshiyuki Okajima

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