From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756338Ab0DUULq (ORCPT ); Wed, 21 Apr 2010 16:11:46 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:41243 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755024Ab0DUULo (ORCPT ); Wed, 21 Apr 2010 16:11:44 -0400 Date: Wed, 21 Apr 2010 13:11:41 -0700 From: "Paul E. McKenney" To: Eric Dumazet Cc: David Howells , torvalds@osdl.org, akpm@linux-foundation.org, keyrings@linux-nfs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KEYS: Fix an RCU warning Message-ID: <20100421201141.GI2563@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20100420102549.31890.6348.stgit@warthog.procyon.org.uk> <1271767564.3845.224.camel@edumazet-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1271767564.3845.224.camel@edumazet-laptop> 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 On Tue, Apr 20, 2010 at 02:46:04PM +0200, Eric Dumazet wrote: > Le mardi 20 avril 2010 à 11:25 +0100, David Howells a écrit : > > Fix the following RCU warning: > > > > =================================================== > > [ INFO: suspicious rcu_dereference_check() usage. ] > > --------------------------------------------------- > > security/keys/request_key.c:116 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/5372: > > #0: (key_types_sem){.+.+.+}, at: [] key_type_lookup+0x1c/0x70 > > > > stack backtrace: > > Pid: 5372, comm: keyctl Not tainted 2.6.34-rc3-cachefs #150 > > Call Trace: > > [] lockdep_rcu_dereference+0xaa/0xb2 > > [] call_sbin_request_key+0x156/0x2b6 > > [] ? __key_instantiate_and_link+0xb1/0xdc > > [] ? key_instantiate_and_link+0x42/0x5f > > [] ? request_key_auth_new+0x17b/0x1f3 > > [] ? request_key_and_link+0x271/0x400 > > [] ? kmem_cache_alloc+0xe1/0x118 > > [] request_key_and_link+0x38b/0x400 > > [] sys_request_key+0xf7/0x14a > > [] ? trace_hardirqs_on_caller+0x10c/0x130 > > [] ? trace_hardirqs_on_thunk+0x3a/0x3f > > [] system_call_fastpath+0x16/0x1b > > > > This was caused by doing: > > > > [root@andromeda ~]# keyctl newring fred @s > > 539196288 > > [root@andromeda ~]# keyctl request2 user a a 539196288 > > request_key: Required key not available > > > > Signed-off-by: David Howells > > --- > > > > Acked-by: Eric Dumazet > > Thanks ! Queued for 2.6.34, thank you both! Thanx, Paul > > security/keys/request_key.c | 13 ++++++++----- > > 1 files changed, 8 insertions(+), 5 deletions(-) > > > > diff --git a/security/keys/request_key.c b/security/keys/request_key.c > > index 03fe63e..ea97c31 100644 > > --- a/security/keys/request_key.c > > +++ b/security/keys/request_key.c > > @@ -68,7 +68,8 @@ static int call_sbin_request_key(struct key_construction *cons, > > { > > const struct cred *cred = current_cred(); > > key_serial_t prkey, sskey; > > - struct key *key = cons->key, *authkey = cons->authkey, *keyring; > > + struct key *key = cons->key, *authkey = cons->authkey, *keyring, > > + *session; > > char *argv[9], *envp[3], uid_str[12], gid_str[12]; > > char key_str[12], keyring_str[3][12]; > > char desc[20]; > > @@ -112,10 +113,12 @@ static int call_sbin_request_key(struct key_construction *cons, > > if (cred->tgcred->process_keyring) > > prkey = cred->tgcred->process_keyring->serial; > > > > - if (cred->tgcred->session_keyring) > > - sskey = rcu_dereference(cred->tgcred->session_keyring)->serial; > > - else > > - sskey = cred->user->session_keyring->serial; > > + rcu_read_lock(); > > + session = rcu_dereference(cred->tgcred->session_keyring); > > + if (!session) > > + session = cred->user->session_keyring; > > + sskey = session->serial; > > + rcu_read_unlock(); > > > > sprintf(keyring_str[2], "%d", sskey); > > > > > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/