From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757018Ab0ECWEe (ORCPT ); Mon, 3 May 2010 18:04:34 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:48825 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753338Ab0ECWEc (ORCPT ); Mon, 3 May 2010 18:04:32 -0400 Date: Mon, 3 May 2010 17:04:20 -0500 From: "Serge E. Hallyn" To: David Howells Cc: torvalds@osdl.org, akpm@linux-foundation.org, keyrings@linux-nfs.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/7] KEYS: Fix an RCU warning in the reading of user keys Message-ID: <20100503220420.GA6968@us.ibm.com> References: <20100430133208.2126.56765.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100430133208.2126.56765.stgit@warthog.procyon.org.uk> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting David Howells (dhowells@redhat.com): > Fix an RCU warning in the reading of user keys: > > =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > security/keys/user_defined.c:202 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > > rcu_scheduler_active = 1, debug_locks = 0 > 1 lock held by keyctl/3637: > #0: (&key->sem){+++++.}, at: [] keyctl_read_key+0x9c/0xcf > > stack backtrace: > Pid: 3637, comm: keyctl Not tainted 2.6.34-rc5-cachefs #18 > Call Trace: > [] lockdep_rcu_dereference+0xaa/0xb2 > [] user_read+0x47/0x91 > [] keyctl_read_key+0xac/0xcf > [] sys_keyctl+0x75/0xb7 > [] system_call_fastpath+0x16/0x1b > > Signed-off-by: David Howells heck it also serves to document it a bit, as looking at the fn itself it's not clear that it is called under key->sem. Acked-by: Serge Hallyn > --- > > security/keys/user_defined.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c > index 7c687d5..e9aa079 100644 > --- a/security/keys/user_defined.c > +++ b/security/keys/user_defined.c > @@ -199,7 +199,8 @@ long user_read(const struct key *key, char __user *buffer, size_t buflen) > struct user_key_payload *upayload; > long ret; > > - upayload = rcu_dereference(key->payload.data); > + upayload = rcu_dereference_protected( > + key->payload.data, rwsem_is_locked(&((struct key *)key)->sem)); > ret = upayload->datalen; > > /* we can return the data as is */ > > -- > To unsubscribe from this list: send the line "unsubscribe linux-security-module" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html