[PATCH 1/2] CRED: Fix BUG() upon security_cred_alloc_blank() failure

[PATCH 1/2] CRED: Fix BUG() upon security_cred_alloc_blank() failure

[David Howells]

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

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@I-love.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 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);
 }

[PATCH 2/2] CRED: Fix memory and refcount leaks upon security_prepare_creds() failure

[David Howells]

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

In prepare_kernel_cred() since 2.6.29, put_cred(new) is called without
assigning new->usage when security_prepare_creds() returned an error.  As a
result, memory for new and refcount for new->{user,group_info,tgcred} are
leaked because put_cred(new) won't call __put_cred() unless old->usage == 1.

Fix these leaks by assigning new->usage (and new->subscribers which was added
in 2.6.32) before calling security_prepare_creds().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 kernel/cred.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index fcf104b..3a9d6dd 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -657,6 +657,8 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	validate_creds(old);
 
 	*new = *old;
+	atomic_set(&new->usage, 1);
+	set_cred_subscribers(new, 0);
 	get_uid(new->user);
 	get_group_info(new->group_info);
 
@@ -674,8 +676,6 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 		goto error;
 
-	atomic_set(&new->usage, 1);
-	set_cred_subscribers(new, 0);
 	put_cred(old);
 	validate_creds(new);
 	return new;

Re: [PATCH 1/2] CRED: Fix BUG() upon security_cred_alloc_blank() failure

[Andrew Morton]

On Mon, 07 Feb 2011 13:36:10 +0000
David Howells <dhowells@redhat.com> wrote:

> 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().

You don't feel that these two patches should be backported into -stable?

[PATCH 1/2] CRED: Fix BUG() upon security_cred_alloc_blank() failure

[David Howells]

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

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@I-love.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 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);
 }

[PATCH 2/2] CRED: Fix memory and refcount leaks upon security_prepare_creds() failure

[David Howells]

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

In prepare_kernel_cred() since 2.6.29, put_cred(new) is called without
assigning new->usage when security_prepare_creds() returned an error.  As a
result, memory for new and refcount for new->{user,group_info,tgcred} are
leaked because put_cred(new) won't call __put_cred() unless old->usage == 1.

Fix these leaks by assigning new->usage (and new->subscribers which was added
in 2.6.32) before calling security_prepare_creds().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
---

 kernel/cred.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index fcf104b..3a9d6dd 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -657,6 +657,8 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	validate_creds(old);
 
 	*new = *old;
+	atomic_set(&new->usage, 1);
+	set_cred_subscribers(new, 0);
 	get_uid(new->user);
 	get_group_info(new->group_info);
 
@@ -674,8 +676,6 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
 		goto error;
 
-	atomic_set(&new->usage, 1);
-	set_cred_subscribers(new, 0);
 	put_cred(old);
 	validate_creds(new);
 	return new;