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From: "Serge E. Hallyn" <serue@us.ibm.com>
To: David Howells <dhowells@redhat.com>
Cc: torvalds@osdl.org, akpm@linux-foundation.org,
	paulmck@linux.vnet.ibm.com, keyrings@linux-nfs.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KEYS: Fix RCU handling in key_gc_keyring()
Date: Tue, 4 May 2010 10:46:01 -0500	[thread overview]
Message-ID: <20100504154601.GA20291@us.ibm.com> (raw)
In-Reply-To: <20100504131610.2015.50934.stgit@warthog.procyon.org.uk>

Quoting David Howells (dhowells@redhat.com):
> key_gc_keyring() needs to either hold the RCU read lock or hold the keyring
> semaphore if it's going to scan the keyring's list.  Given that it only needs
> to read the key list, and it's doing so under a spinlock, the RCU read lock is
> the thing to use.
> 
> Furthermore, the RCU check added in e7b0a61b7929632d36cf052d9e2820ef0a9c1bfe is
> incorrect as holding the spinlock on key_serial_lock is not grounds for
> assuming a keyring's pointer list can be read safely.  Instead, a simple
> rcu_dereference() inside of the previously mentioned RCU read lock is what we
> want.
> 
> Reported-by: Serge E. Hallyn <serue@us.ibm.com>

You're obviously being far too kind.  In apparent trend for last night
I missed the lack of locking here.

> Signed-off-by: David Howells <dhowells@redhat.com>

Acked-by: Serge Hallyn <serue@us.ibm.com>

thanks,
-serge

  reply	other threads:[~2010-05-04 15:46 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-04 13:16 [PATCH] KEYS: Fix RCU handling in key_gc_keyring() David Howells
2010-05-04 15:46 ` Serge E. Hallyn [this message]
2010-05-04 15:58   ` David Howells
2010-05-05  0:59 ` Paul E. McKenney
2010-05-05  9:31   ` David Howells

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