From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754578Ab0DTMqN (ORCPT ); Tue, 20 Apr 2010 08:46:13 -0400 Received: from mail-bw0-f219.google.com ([209.85.218.219]:58144 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754537Ab0DTMqM (ORCPT ); Tue, 20 Apr 2010 08:46:12 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=XxSucxejfwRMDR5nREu+QXj8dGv2CJjU+CU3fAWrpGp+6S3erVfBCnlY+eQx9FIF4g K8qEmeyG+oP3OI9RfSxIVtRTIcnLg1kD5BeljqqinY/Dqk6c6eGhbJkmKhbpRTRNTi7B gX6xYeTAaPFYzippBBZ3uIHsk88cpmzAMlbis= Subject: Re: [PATCH] KEYS: Fix an RCU warning From: Eric Dumazet To: David Howells Cc: torvalds@osdl.org, akpm@linux-foundation.org, keyrings@linux-nfs.org, linux-kernel@vger.kernel.org In-Reply-To: <20100420102549.31890.6348.stgit@warthog.procyon.org.uk> References: <20100420102549.31890.6348.stgit@warthog.procyon.org.uk> Content-Type: text/plain; charset="UTF-8" Date: Tue, 20 Apr 2010 14:46:04 +0200 Message-ID: <1271767564.3845.224.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ! > 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); > >