From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755389Ab1BGX47 (ORCPT ); Mon, 7 Feb 2011 18:56:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34378 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755193Ab1BGX45 (ORCPT ); Mon, 7 Feb 2011 18:56:57 -0500 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20110207133610.18389.5602.stgit@warthog.procyon.org.uk> References: <20110207133610.18389.5602.stgit@warthog.procyon.org.uk> To: stable@kernel.org Cc: dhowells@redhat.com, akpm@linux-foundation.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Tetsuo Handa Subject: [PATCH 1/2] CRED: Fix BUG() upon security_cred_alloc_blank() failure Date: Mon, 07 Feb 2011 23:56:32 +0000 Message-ID: <13689.1297122992@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tetsuo Handa In cred_alloc_blank() since 2.6.32, abort_creds(new) is called with new->security == NULL and new->magic == 0 when security_cred_alloc_blank() returns an error. As a result, BUG() will be triggered if SELinux is enabled or CONFIG_DEBUG_CREDENTIALS=y. If CONFIG_DEBUG_CREDENTIALS=y, BUG() is called from __invalid_creds() because cred->magic == 0. Failing that, BUG() is called from selinux_cred_free() because selinux_cred_free() is not expecting cred->security == NULL. This does not affect smack_cred_free(), tomoyo_cred_free() or apparmor_cred_free(). Fix these bugs by (1) Set new->magic before calling security_cred_alloc_blank(). (2) Handle null cred->security in creds_are_invalid() and selinux_cred_free(). Signed-off-by: Tetsuo Handa Signed-off-by: David Howells --- kernel/cred.c | 12 ++++++++---- security/selinux/hooks.c | 6 +++++- 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/kernel/cred.c b/kernel/cred.c index 6a1aa00..fcf104b 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -252,13 +252,13 @@ struct cred *cred_alloc_blank(void) #endif atomic_set(&new->usage, 1); +#ifdef CONFIG_DEBUG_CREDENTIALS + new->magic = CRED_MAGIC; +#endif if (security_cred_alloc_blank(new, GFP_KERNEL) < 0) goto error; -#ifdef CONFIG_DEBUG_CREDENTIALS - new->magic = CRED_MAGIC; -#endif return new; error: @@ -748,7 +748,11 @@ bool creds_are_invalid(const struct cred *cred) if (cred->magic != CRED_MAGIC) return true; #ifdef CONFIG_SECURITY_SELINUX - if (selinux_is_enabled()) { + /* + * cred->security == NULL if security_cred_alloc_blank() or + * security_prepare_creds() returned an error. + */ + if (selinux_is_enabled() && cred->security) { if ((unsigned long) cred->security < PAGE_SIZE) return true; if ((*(u32 *)cred->security & 0xffffff00) == diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index e276eb4..c8d6992 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3198,7 +3198,11 @@ static void selinux_cred_free(struct cred *cred) { struct task_security_struct *tsec = cred->security; - BUG_ON((unsigned long) cred->security < PAGE_SIZE); + /* + * cred->security == NULL if security_cred_alloc_blank() or + * security_prepare_creds() returned an error. + */ + BUG_ON(cred->security && (unsigned long) cred->security < PAGE_SIZE); cred->security = (void *) 0x7UL; kfree(tsec); }