linux-kernel - [PATCH] [120/275] CRED: Fix BUG() upon security_cred_alloc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 30 Mar 2011 14:06:00 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	penguin-kernel@...ove.SAKURA.ne.jp, dhowells@...hat.com,
	torvalds@...ux-foundation.org, gregkh@...e.de, ak@...ux.intel.com,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	tim.bird@...sony.com
Subject: [PATCH] [120/275] CRED: Fix BUG() upon security_cred_alloc_blank() failure

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

commit 2edeaa34a6e3f2c43b667f6c4f7b27944b811695 upstream.

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 <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 kernel/cred.c            |   12 ++++++++----
 security/selinux/hooks.c |    6 +++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

Index: linux-2.6.35.y/kernel/cred.c
===================================================================
--- linux-2.6.35.y.orig/kernel/cred.c	2011-03-29 22:51:20.320203225 -0700
+++ linux-2.6.35.y/kernel/cred.c	2011-03-29 23:54:51.139693889 -0700
@@ -256,13 +256,13 @@
 #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:
@@ -754,7 +754,11 @@
 	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) ==
Index: linux-2.6.35.y/security/selinux/hooks.c
===================================================================
--- linux-2.6.35.y.orig/security/selinux/hooks.c	2011-03-29 23:02:59.725307200 -0700
+++ linux-2.6.35.y/security/selinux/hooks.c	2011-03-29 23:03:00.712281944 -0700
@@ -3234,7 +3234,11 @@
 {
 	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);
 }
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/