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[PATCH 0/6] LSM: Security module blob management

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  [PATCH 0/6] LSM: Security module blob management Casey Schaufler <casey@schaufler-ca.com> - 2017-06-08 22:50 +0200
    [PATCH 3/6] LSM: Manage file security blobs Casey Schaufler <casey@schaufler-ca.com> - 2017-06-08 23:00 +0200
    [PATCH 4/6] LSM: manage task security blobs Casey Schaufler <casey@schaufler-ca.com> - 2017-06-08 23:00 +0200
    [PATCH 1/6] procfs-add-smack-subdir-to-attrs Casey Schaufler <casey@schaufler-ca.com> - 2017-06-08 23:00 +0200
    [PATCH 6/6] LSM: general but not extreme module stacking Casey Schaufler <casey@schaufler-ca.com> - 2017-06-08 23:00 +0200
    Re: [kernel-hardening] [PATCH 0/6] LSM: Security module blob  management Matt Brown <matt@nmatt.com> - 2017-06-08 23:00 +0200
      Re: [kernel-hardening] [PATCH 0/6] LSM: Security module blob  management James Morris <jmorris@namei.org> - 2017-06-09 06:00 +0200

#1661673 — [PATCH 0/6] LSM: Security module blob management

Subject: [PATCH 0/6] LSM: Security module blob management

This patch set moves management of security blobs out of
the Linux security modules and into the security module
infrastructure. This allows "major" security modules that
use blobs to be stacked, just as "minor" modules that
do not use blobs can be stacked today. It stops short of
providing a safe interface for the Netlabel and SO_PEERSEC.
As a result, any of the existing security modules may be
used in combination except for SELinux and Smack.

The result passes the SELinux testsuite for the significant
number of configurations tried, and fails none of them.
Smack tests went swimmingly as well. AppArmor was boot
tested with Ubuntu 17.04.

There is work in a separate project to make Smack a better
user of the Netlabel subsystem, which is needed to allow
for a rational Netlabel configuration when both SELinux
and Smack are active at the same time. That will be the
next phase of the stacking project, and is nearing
completion. I stopped short of including that work here
because it's not required by any of the new security
modules that I know are waiting for "major" stacking.

Patch 1/6: Creates a subdir for Smack in /proc/.../attr.
           This has been submitted as an enhancement for
           Smack, as it cleans up Smack userspace.
Patch 2/6: Introduces infrastructure management of the
           credential (cred->security) blob
Patch 3/6: Introduces infrastructure management of the
           file (file->f_security) blob
Patch 4/6: Introduces infrastructure management of the
           new task (task->security) blob
Patch 5/6: Introduces infrastructure management of the
           remaining security blobs, including the inode,
           socket, superblock and IPC object blobs.
Patch 6/6: Changes the Kconfig in the security subsystem
           to define a module stack instead of a choice
           of a single module. Adds /proc/.../attr
           subdirectories for AppArmor and SELinux. Adds
           a "context" attr file to provide a combined
           view of the process security attributes.

These patches can be found in git at:

	https://github.com/cschaufler/smack-next.git#stacking-4.12-rc2

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 Documentation/security/LSM.txt      |  33 +-
 fs/proc/base.c                      |  96 +++++-
 fs/proc/internal.h                  |   1 +
 include/linux/lsm_hooks.h           |  26 +-
 include/linux/security.h            |  15 +-
 kernel/cred.c                       |  13 -
 security/Kconfig                    | 105 +++++++
 security/apparmor/context.c         |   2 -
 security/apparmor/include/context.h |  25 +-
 security/apparmor/lsm.c             | 111 ++++---
 security/security.c                 | 587 +++++++++++++++++++++++++++++++++++-
 security/selinux/hooks.c            | 513 +++++++++++--------------------
 security/selinux/include/objsec.h   |  87 +++++-
 security/selinux/netlabel.c         |  15 +-
 security/selinux/selinuxfs.c        |   5 +-
 security/selinux/ss/services.c      |   3 +-
 security/selinux/xfrm.c             |   4 +-
 security/smack/smack.h              |  90 +++++-
 security/smack/smack_access.c       |   2 +-
 security/smack/smack_lsm.c          | 526 +++++++++++---------------------
 security/smack/smack_netfilter.c    |   8 +-
 security/smack/smackfs.c            |  18 +-
 security/tomoyo/common.h            |  30 +-
 security/tomoyo/domain.c            |   4 +-
 security/tomoyo/securityfs_if.c     |  13 +-
 security/tomoyo/tomoyo.c            |  52 +++-
 26 files changed, 1540 insertions(+), 844 deletions(-)

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#1661680 — [PATCH 3/6] LSM: Manage file security blobs

Subject: [PATCH 3/6] LSM: Manage file security blobs

Move the management of file security blobs from the individual
security modules to the security infrastructure. The security modules
using file blobs have been updated accordingly. Modules are required
to identify the space they need at module initialization. In some
cases a module no longer needs to supply a blob management hook, in
which case the hook has been removed.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/linux/lsm_hooks.h           |  1 +
 security/apparmor/include/context.h |  6 ++++++
 security/apparmor/lsm.c             | 26 ++++-------------------
 security/security.c                 | 32 +++++++++++++++++++++++++++++
 security/selinux/hooks.c            | 41 +++++++++----------------------------
 security/selinux/include/objsec.h   |  5 +++++
 security/smack/smack.h              |  5 +++++
 security/smack/smack_lsm.c          | 26 ++++++++---------------
 8 files changed, 72 insertions(+), 70 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 41f01e2..dc012eb 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1894,6 +1894,7 @@ struct security_hook_list {
  */
 struct lsm_blob_sizes {
 	int	lbs_cred;
+	int	lbs_file;
 };
 
 /*
diff --git a/security/apparmor/include/context.h b/security/apparmor/include/context.h
index f35ad39..3ff3879 100644
--- a/security/apparmor/include/context.h
+++ b/security/apparmor/include/context.h
@@ -25,6 +25,7 @@
 
 #define cred_ctx(X) apparmor_cred(X)
 #define current_ctx() cred_ctx(current_cred())
+#define file_ctx(X) apparmor_file(X)
 
 /* struct aa_file_ctx - the AppArmor context the file was opened in
  * @perms: the permission the file was opened with
@@ -92,6 +93,11 @@ static inline struct aa_task_ctx *apparmor_cred(const struct cred *cred)
 	return cred->security;
 }
 
+static inline struct aa_file_ctx *apparmor_file(const struct file *file)
+{
+	return file->f_security;
+}
+
 /**
  * aa_cred_profile - obtain cred's profiles
  * @cred: cred to obtain profiles from  (NOT NULL)
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index eef5551..12a0265 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -329,7 +329,7 @@ static int apparmor_inode_getattr(const struct path *path)
 
 static int apparmor_file_open(struct file *file, const struct cred *cred)
 {
-	struct aa_file_ctx *fctx = file->f_security;
+	struct aa_file_ctx *fctx = file_ctx(file);
 	struct aa_profile *profile;
 	int error = 0;
 
@@ -360,26 +360,9 @@ static int apparmor_file_open(struct file *file, const struct cred *cred)
 	return error;
 }
 
-static int apparmor_file_alloc_security(struct file *file)
-{
-	/* freed by apparmor_file_free_security */
-	file->f_security = aa_alloc_file_context(GFP_KERNEL);
-	if (!file->f_security)
-		return -ENOMEM;
-	return 0;
-
-}
-
-static void apparmor_file_free_security(struct file *file)
-{
-	struct aa_file_ctx *ctx = file->f_security;
-
-	aa_free_file_context(ctx);
-}
-
 static int common_file_perm(const char *op, struct file *file, u32 mask)
 {
-	struct aa_file_ctx *fctx = file->f_security;
+	struct aa_file_ctx *fctx = file_ctx(file);
 	struct aa_profile *profile, *fprofile = aa_cred_profile(file->f_cred);
 	int error = 0;
 
@@ -425,7 +408,7 @@ static int common_mmap(const char *op, struct file *file, unsigned long prot,
 {
 	int mask = 0;
 
-	if (!file || !file->f_security)
+	if (!file || file_ctx(file) == NULL)
 		return 0;
 
 	if (prot & PROT_READ)
@@ -566,6 +549,7 @@ static int apparmor_task_setrlimit(struct task_struct *task,
 
 struct lsm_blob_sizes apparmor_blob_sizes = {
 	.lbs_cred = sizeof(struct aa_task_ctx),
+	.lbs_file = sizeof(struct aa_file_ctx),
 };
 
 static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
@@ -588,8 +572,6 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(file_open, apparmor_file_open),
 	LSM_HOOK_INIT(file_permission, apparmor_file_permission),
-	LSM_HOOK_INIT(file_alloc_security, apparmor_file_alloc_security),
-	LSM_HOOK_INIT(file_free_security, apparmor_file_free_security),
 	LSM_HOOK_INIT(mmap_file, apparmor_mmap_file),
 	LSM_HOOK_INIT(file_mprotect, apparmor_file_mprotect),
 	LSM_HOOK_INIT(file_lock, apparmor_file_lock),
diff --git a/security/security.c b/security/security.c
index 062a9e4..3c22fb1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -88,6 +88,7 @@ int __init security_init(void)
 
 #ifdef CONFIG_SECURITY_LSM_DEBUG
 	pr_info("LSM: cred blob size       = %d\n", blob_sizes.lbs_cred);
+	pr_info("LSM: file blob size       = %d\n", blob_sizes.lbs_file);
 #endif
 
 	return 0;
@@ -246,6 +247,30 @@ static void __init lsm_set_size(int *need, int *lbs)
 void __init security_add_blobs(struct lsm_blob_sizes *needed)
 {
 	lsm_set_size(&needed->lbs_cred, &blob_sizes.lbs_cred);
+	lsm_set_size(&needed->lbs_file, &blob_sizes.lbs_file);
+}
+
+/**
+ * lsm_file_alloc - allocate a composite file blob
+ * @file: the file that needs a blob
+ *
+ * Allocate the file blob for all the modules
+ *
+ * Returns 0, or -ENOMEM if memory can't be allocated.
+ */
+int lsm_file_alloc(struct file *file)
+{
+#ifdef CONFIG_SECURITY_LSM_DEBUG
+	if (file->f_security)
+		pr_info("%s: Inbound file blob is not NULL.\n", __func__);
+#endif
+	if (blob_sizes.lbs_file == 0)
+		return 0;
+
+	file->f_security = kzalloc(blob_sizes.lbs_file, GFP_KERNEL);
+	if (file->f_security == NULL)
+		return -ENOMEM;
+	return 0;
 }
 
 /*
@@ -933,12 +958,19 @@ int security_file_permission(struct file *file, int mask)
 
 int security_file_alloc(struct file *file)
 {
+	int rc = lsm_file_alloc(file);
+
+	if (rc)
+		return rc;
 	return call_int_hook(file_alloc_security, 0, file);
 }
 
 void security_file_free(struct file *file)
 {
 	call_void_hook(file_free_security, file);
+
+	kfree(file->f_security);
+	file->f_security = NULL;
 }
 
 int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 00156c6..223a178 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -127,7 +127,6 @@ int selinux_enabled = 1;
 #endif
 
 static struct kmem_cache *sel_inode_cache;
-static struct kmem_cache *file_security_cache;
 
 /**
  * selinux_secmark_enabled - Check to see if SECMARK is currently enabled
@@ -347,27 +346,15 @@ static void inode_free_security(struct inode *inode)
 
 static int file_alloc_security(struct file *file)
 {
-	struct file_security_struct *fsec;
+	struct file_security_struct *fsec = selinux_file(file);
 	u32 sid = current_sid();
 
-	fsec = kmem_cache_zalloc(file_security_cache, GFP_KERNEL);
-	if (!fsec)
-		return -ENOMEM;
-
 	fsec->sid = sid;
 	fsec->fown_sid = sid;
-	file->f_security = fsec;
 
 	return 0;
 }
 
-static void file_free_security(struct file *file)
-{
-	struct file_security_struct *fsec = file->f_security;
-	file->f_security = NULL;
-	kmem_cache_free(file_security_cache, fsec);
-}
-
 static int superblock_alloc_security(struct super_block *sb)
 {
 	struct superblock_security_struct *sbsec;
@@ -1793,7 +1780,7 @@ static int file_has_perm(const struct cred *cred,
 			 struct file *file,
 			 u32 av)
 {
-	struct file_security_struct *fsec = file->f_security;
+	struct file_security_struct *fsec = selinux_file(file);
 	struct inode *inode = file_inode(file);
 	struct common_audit_data ad;
 	u32 sid = cred_sid(cred);
@@ -2112,7 +2099,7 @@ static int selinux_binder_transfer_file(struct task_struct *from,
 					struct file *file)
 {
 	u32 sid = task_sid(to);
-	struct file_security_struct *fsec = file->f_security;
+	struct file_security_struct *fsec = selinux_file(file);
 	struct dentry *dentry = file->f_path.dentry;
 	struct inode_security_struct *isec;
 	struct common_audit_data ad;
@@ -3376,7 +3363,7 @@ static int selinux_revalidate_file_permission(struct file *file, int mask)
 static int selinux_file_permission(struct file *file, int mask)
 {
 	struct inode *inode = file_inode(file);
-	struct file_security_struct *fsec = file->f_security;
+	struct file_security_struct *fsec = selinux_file(file);
 	struct inode_security_struct *isec;
 	u32 sid = current_sid();
 
@@ -3398,11 +3385,6 @@ static int selinux_file_alloc_security(struct file *file)
 	return file_alloc_security(file);
 }
 
-static void selinux_file_free_security(struct file *file)
-{
-	file_free_security(file);
-}
-
 /*
  * Check whether a task has the ioctl permission and cmd
  * operation to an inode.
@@ -3411,7 +3393,7 @@ static int ioctl_has_perm(const struct cred *cred, struct file *file,
 		u32 requested, u16 cmd)
 {
 	struct common_audit_data ad;
-	struct file_security_struct *fsec = file->f_security;
+	struct file_security_struct *fsec = selinux_file(file);
 	struct inode *inode = file_inode(file);
 	struct inode_security_struct *isec;
 	struct lsm_ioctlop_audit ioctl;
@@ -3645,7 +3627,7 @@ static void selinux_file_set_fowner(struct file *file)
 {
 	struct file_security_struct *fsec;
 
-	fsec = file->f_security;
+	fsec = selinux_file(file);
 	fsec->fown_sid = current_sid();
 }
 
@@ -3660,7 +3642,7 @@ static int selinux_file_send_sigiotask(struct task_struct *tsk,
 	/* struct fown_struct is never outside the context of a struct file */
 	file = container_of(fown, struct file, f_owner);
 
-	fsec = file->f_security;
+	fsec = selinux_file(file);
 
 	if (!signum)
 		perm = signal_to_av(SIGIO); /* as per send_sigio_to_task */
@@ -3683,7 +3665,7 @@ static int selinux_file_open(struct file *file, const struct cred *cred)
 	struct file_security_struct *fsec;
 	struct inode_security_struct *isec;
 
-	fsec = file->f_security;
+	fsec = selinux_file(file);
 	isec = inode_security(file_inode(file));
 	/*
 	 * Save inode label and policy sequence number
@@ -3812,7 +3794,7 @@ static int selinux_kernel_module_from_file(struct file *file)
 	ad.type = LSM_AUDIT_DATA_FILE;
 	ad.u.file = file;
 
-	fsec = file->f_security;
+	fsec = selinux_file(file);
 	if (sid != fsec->sid) {
 		rc = avc_has_perm(sid, fsec->sid, SECCLASS_FD, FD__USE, &ad);
 		if (rc)
@@ -6094,6 +6076,7 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
 
 struct lsm_blob_sizes selinux_blob_sizes = {
 	.lbs_cred = sizeof(struct task_security_struct),
+	.lbs_file = sizeof(struct file_security_struct),
 };
 
 static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
@@ -6165,7 +6148,6 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(file_permission, selinux_file_permission),
 	LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
-	LSM_HOOK_INIT(file_free_security, selinux_file_free_security),
 	LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),
 	LSM_HOOK_INIT(mmap_file, selinux_mmap_file),
 	LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr),
@@ -6340,9 +6322,6 @@ static __init int selinux_init(void)
 	sel_inode_cache = kmem_cache_create("selinux_inode_security",
 					    sizeof(struct inode_security_struct),
 					    0, SLAB_PANIC, NULL);
-	file_security_cache = kmem_cache_create("selinux_file_security",
-					    sizeof(struct file_security_struct),
-					    0, SLAB_PANIC, NULL);
 	avc_init();
 
 	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index 48132cc..6a638da 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -150,4 +150,9 @@ static inline struct task_security_struct *selinux_cred(const struct cred *cred)
 	return cred->security;
 }
 
+static inline struct file_security_struct *selinux_file(const struct file *file)
+{
+	return file->f_security;
+}
+
 #endif /* _SELINUX_OBJSEC_H_ */
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 17949ec..9e704a6 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -361,6 +361,11 @@ static inline struct task_smack *smack_cred(const struct cred *cred)
 	return cred->security;
 }
 
+static inline struct smack_known **smack_file(const struct file *file)
+{
+	return file->f_security;
+}
+
 /*
  * Is the directory transmuting?
  */
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 3ee5a14..3c95c1f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1601,25 +1601,13 @@ static void smack_inode_getsecid(struct inode *inode, u32 *secid)
  */
 static int smack_file_alloc_security(struct file *file)
 {
-	struct smack_known *skp = smk_of_current();
+	struct smack_known **blob = smack_file(file);
 
-	file->f_security = skp;
+	*blob = smk_of_current();
 	return 0;
 }
 
 /**
- * smack_file_free_security - clear a file security blob
- * @file: the object
- *
- * The security blob for a file is a pointer to the master
- * label list, so no memory is freed.
- */
-static void smack_file_free_security(struct file *file)
-{
-	file->f_security = NULL;
-}
-
-/**
  * smack_file_ioctl - Smack check on ioctls
  * @file: the object
  * @cmd: what to do
@@ -1843,7 +1831,9 @@ static int smack_mmap_file(struct file *file,
  */
 static void smack_file_set_fowner(struct file *file)
 {
-	file->f_security = smk_of_current();
+	struct smack_known **blob = smack_file(file);
+
+	*blob = smk_of_current();
 }
 
 /**
@@ -1860,6 +1850,7 @@ static void smack_file_set_fowner(struct file *file)
 static int smack_file_send_sigiotask(struct task_struct *tsk,
 				     struct fown_struct *fown, int signum)
 {
+	struct smack_known **blob;
 	struct smack_known *skp;
 	struct smack_known *tkp = smk_of_task(smack_cred(tsk->cred));
 	struct file *file;
@@ -1872,7 +1863,8 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
 	file = container_of(fown, struct file, f_owner);
 
 	/* we don't log here as rc can be overriden */
-	skp = file->f_security;
+	blob = smack_file(file);
+	skp = *blob;
 	rc = smk_access(skp, tkp, MAY_DELIVER, NULL);
 	rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);
 	if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE))
@@ -4604,6 +4596,7 @@ static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
 
 struct lsm_blob_sizes smack_blob_sizes = {
 	.lbs_cred = sizeof(struct task_smack),
+	.lbs_file = sizeof(struct smack_known *),
 };
 
 static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
@@ -4643,7 +4636,6 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(inode_getsecid, smack_inode_getsecid),
 
 	LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security),
-	LSM_HOOK_INIT(file_free_security, smack_file_free_security),
 	LSM_HOOK_INIT(file_ioctl, smack_file_ioctl),
 	LSM_HOOK_INIT(file_lock, smack_file_lock),
 	LSM_HOOK_INIT(file_fcntl, smack_file_fcntl),
-- 
2.5.5

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#1661686 — [PATCH 4/6] LSM: manage task security blobs

Subject: [PATCH 4/6] LSM: manage task security blobs

Move management of task security blobs into the security
infrastructure. Modules are required to identify the space
they require. At this time there are no modules that use
task blobs.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 include/linux/lsm_hooks.h |  1 +
 security/security.c       | 28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index dc012eb..feb78e4 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1895,6 +1895,7 @@ struct security_hook_list {
 struct lsm_blob_sizes {
 	int	lbs_cred;
 	int	lbs_file;
+	int	lbs_task;
 };
 
 /*
diff --git a/security/security.c b/security/security.c
index 3c22fb1..bdf8c04 100644
--- a/security/security.c
+++ b/security/security.c
@@ -89,6 +89,7 @@ int __init security_init(void)
 #ifdef CONFIG_SECURITY_LSM_DEBUG
 	pr_info("LSM: cred blob size       = %d\n", blob_sizes.lbs_cred);
 	pr_info("LSM: file blob size       = %d\n", blob_sizes.lbs_file);
+	pr_info("LSM: task blob size       = %d\n", blob_sizes.lbs_task);
 #endif
 
 	return 0;
@@ -248,6 +249,7 @@ void __init security_add_blobs(struct lsm_blob_sizes *needed)
 {
 	lsm_set_size(&needed->lbs_cred, &blob_sizes.lbs_cred);
 	lsm_set_size(&needed->lbs_file, &blob_sizes.lbs_file);
+	lsm_set_size(&needed->lbs_task, &blob_sizes.lbs_task);
 }
 
 /**
@@ -273,6 +275,29 @@ int lsm_file_alloc(struct file *file)
 	return 0;
 }
 
+/**
+ * lsm_task_alloc - allocate a composite task blob
+ * @task: the task that needs a blob
+ *
+ * Allocate the task blob for all the modules
+ *
+ * Returns 0, or -ENOMEM if memory can't be allocated.
+ */
+int lsm_task_alloc(struct task_struct *task)
+{
+#ifdef CONFIG_SECURITY_LSM_DEBUG
+	if (task->security)
+		pr_info("%s: Inbound task blob is not NULL.\n", __func__);
+#endif
+	if (blob_sizes.lbs_task == 0)
+		return 0;
+
+	task->security = kzalloc(blob_sizes.lbs_task, GFP_KERNEL);
+	if (task->security == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
 /*
  * Hook list operation macros.
  *
@@ -1083,6 +1108,9 @@ int security_task_alloc(struct task_struct *task, unsigned long clone_flags)
 void security_task_free(struct task_struct *task)
 {
 	call_void_hook(task_free, task);
+
+	kfree(task->security);
+	task->security = NULL;
 }
 
 int security_cred_alloc_blank(struct cred *cred, gfp_t gfp)
-- 
2.5.5

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#1661688 — [PATCH 1/6] procfs-add-smack-subdir-to-attrs

Subject: [PATCH 1/6] procfs-add-smack-subdir-to-attrs

Back in 2007 I made what turned out to be a rather serious
mistake in the implementation of the Smack security module.
The SELinux module used an interface in /proc to manipulate
the security context on processes. Rather than use a similar
interface, I used the same interface. The AppArmor team did
likewise. Now /proc/.../attr/current will tell you the
security "context" of the process, but it will be different
depending on the security module you're using.

This patch provides a subdirectory in /proc/.../attr for
Smack. Smack user space can use the "current" file in
this subdirectory and never have to worry about getting
SELinux attributes by mistake. Programs that use the
old interface will continue to work (or fail, as the case
may be) as before.

This patch does not include subdirectories for SELinux
or AppArmor. I do have a patch that provides those, and
will happily make it available should anyone see value
in it.

The original implementation is by Kees Cook.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 Documentation/security/LSM.txt | 19 +++++++++----
 fs/proc/base.c                 | 63 ++++++++++++++++++++++++++++++++++++------
 fs/proc/internal.h             |  1 +
 include/linux/security.h       | 15 ++++++----
 security/security.c            | 30 +++++++++++++++++---
 5 files changed, 104 insertions(+), 24 deletions(-)

diff --git a/Documentation/security/LSM.txt b/Documentation/security/LSM.txt
index c2683f2..57eafbc 100644
--- a/Documentation/security/LSM.txt
+++ b/Documentation/security/LSM.txt
@@ -16,11 +16,10 @@ MAC extensions, other extensions can be built using the LSM to provide
 specific changes to system operation when these tweaks are not available
 in the core functionality of Linux itself.
 
-Without a specific LSM built into the kernel, the default LSM will be the
-Linux capabilities system. Most LSMs choose to extend the capabilities
-system, building their checks on top of the defined capability hooks.
-For more details on capabilities, see capabilities(7) in the Linux
-man-pages project.
+The Linux capabilities modules will always be included. For more details
+on capabilities, see capabilities(7) in the Linux man-pages project.
+This may be followed by any number of "minor" modules and at most one
+"major" module.
 
 A list of the active security modules can be found by reading
 /sys/kernel/security/lsm. This is a comma separated list, and
@@ -29,6 +28,14 @@ order in which checks are made. The capability module will always
 be first, followed by any "minor" modules (e.g. Yama) and then
 the one "major" module (e.g. SELinux) if there is one configured.
 
+Process attributes associated with "major" security modules should
+be accessed and maintained using the special files in /proc/.../attr.
+A security module may maintain a module specific subdirectory there,
+named after the module. /proc/.../attr/smack is provided by the Smack
+security module and contains all its special files. The files directly
+in /proc/.../attr remain as legacy interfaces for modules that provide
+subdirectories.
+
 Based on https://lkml.org/lkml/2007/10/26/215,
 a new LSM is accepted into the kernel when its intent (a description of
 what it tries to protect against and in what cases one would expect to
@@ -38,4 +45,4 @@ that end users and distros can make a more informed decision about which
 LSMs suit their requirements.
 
 For extensive documentation on the available LSM hook interfaces, please
-see include/linux/security.h.
+see include/linux/lsm_hooks.h.
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 45f6bf6..10b777a 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -139,9 +139,13 @@ struct pid_entry {
 #define REG(NAME, MODE, fops)				\
 	NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
 #define ONE(NAME, MODE, show)				\
-	NOD(NAME, (S_IFREG|(MODE)), 			\
+	NOD(NAME, (S_IFREG|(MODE)),			\
 		NULL, &proc_single_file_operations,	\
 		{ .proc_show = show } )
+#define ATTR(LSM, NAME, MODE)				\
+	NOD(NAME, (S_IFREG|(MODE)),			\
+		NULL, &proc_pid_attr_operations,	\
+		{ .lsm = LSM })
 
 /*
  * Count the number of hardlinks for the pid_entry table, excluding the .
@@ -2452,7 +2456,7 @@ static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
 	if (!task)
 		return -ESRCH;
 
-	length = security_getprocattr(task,
+	length = security_getprocattr(task, PROC_I(inode)->op.lsm,
 				      (char*)file->f_path.dentry->d_name.name,
 				      &p);
 	put_task_struct(task);
@@ -2498,7 +2502,8 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
 	if (length < 0)
 		goto out_free;
 
-	length = security_setprocattr(file->f_path.dentry->d_name.name,
+	length = security_setprocattr(PROC_I(inode)->op.lsm,
+				      file->f_path.dentry->d_name.name,
 				      page, count);
 	mutex_unlock(&current->signal->cred_guard_mutex);
 out_free:
@@ -2515,13 +2520,53 @@ static const struct file_operations proc_pid_attr_operations = {
 	.llseek		= generic_file_llseek,
 };
 
+#define LSM_DIR_OPS(LSM) \
+static int proc_##LSM##_attr_dir_iterate(struct file *filp, \
+			     struct dir_context *ctx) \
+{ \
+	return proc_pident_readdir(filp, ctx, \
+				   LSM##_attr_dir_stuff, \
+				   ARRAY_SIZE(LSM##_attr_dir_stuff)); \
+} \
+\
+static const struct file_operations proc_##LSM##_attr_dir_ops = { \
+	.read		= generic_read_dir, \
+	.iterate	= proc_##LSM##_attr_dir_iterate, \
+	.llseek		= default_llseek, \
+}; \
+\
+static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \
+				struct dentry *dentry, unsigned int flags) \
+{ \
+	return proc_pident_lookup(dir, dentry, \
+				  LSM##_attr_dir_stuff, \
+				  ARRAY_SIZE(LSM##_attr_dir_stuff)); \
+} \
+\
+static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
+	.lookup		= proc_##LSM##_attr_dir_lookup, \
+	.getattr	= pid_getattr, \
+	.setattr	= proc_setattr, \
+}
+
+#ifdef CONFIG_SECURITY_SMACK
+static const struct pid_entry smack_attr_dir_stuff[] = {
+	ATTR("smack", "current",	0666),
+};
+LSM_DIR_OPS(smack);
+#endif
+
 static const struct pid_entry attr_dir_stuff[] = {
-	REG("current",    S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("prev",       S_IRUGO,	   proc_pid_attr_operations),
-	REG("exec",       S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("fscreate",   S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("keycreate",  S_IRUGO|S_IWUGO, proc_pid_attr_operations),
-	REG("sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
+	ATTR(NULL, "current",		0666),
+	ATTR(NULL, "prev",		0444),
+	ATTR(NULL, "exec",		0666),
+	ATTR(NULL, "fscreate",		0666),
+	ATTR(NULL, "keycreate",		0666),
+	ATTR(NULL, "sockcreate",	0666),
+#ifdef CONFIG_SECURITY_SMACK
+	DIR("smack",			0555,
+	    proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
+#endif
 };
 
 static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index c5ae09b..8b7d101 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -58,6 +58,7 @@ union proc_op {
 	int (*proc_show)(struct seq_file *m,
 		struct pid_namespace *ns, struct pid *pid,
 		struct task_struct *task);
+	const char *lsm;
 };
 
 struct proc_inode {
diff --git a/include/linux/security.h b/include/linux/security.h
index af675b5..8ee9dbd 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -365,8 +365,10 @@ int security_sem_semctl(struct sem_array *sma, int cmd);
 int security_sem_semop(struct sem_array *sma, struct sembuf *sops,
 			unsigned nsops, int alter);
 void security_d_instantiate(struct dentry *dentry, struct inode *inode);
-int security_getprocattr(struct task_struct *p, char *name, char **value);
-int security_setprocattr(const char *name, void *value, size_t size);
+int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
+			 char **value);
+int security_setprocattr(const char *lsm, const char *name, void *value,
+			 size_t size);
 int security_netlink_send(struct sock *sk, struct sk_buff *skb);
 int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
@@ -1111,15 +1113,18 @@ static inline int security_sem_semop(struct sem_array *sma,
 	return 0;
 }
 
-static inline void security_d_instantiate(struct dentry *dentry, struct inode *inode)
+static inline void security_d_instantiate(struct dentry *dentry,
+					  struct inode *inode)
 { }
 
-static inline int security_getprocattr(struct task_struct *p, char *name, char **value)
+static inline int security_getprocattr(struct task_struct *p, const char *lsm,
+				       char *name, char **value)
 {
 	return -EINVAL;
 }
 
-static inline int security_setprocattr(char *name, void *value, size_t size)
+static inline int security_setprocattr(const char *lsm, char *name,
+				       void *value, size_t size)
 {
 	return -EINVAL;
 }
diff --git a/security/security.c b/security/security.c
index 38316bb..e50484c 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1239,14 +1239,36 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
 }
 EXPORT_SYMBOL(security_d_instantiate);
 
-int security_getprocattr(struct task_struct *p, char *name, char **value)
+int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
+				char **value)
 {
-	return call_int_hook(getprocattr, -EINVAL, p, name, value);
+	struct security_hook_list *hp;
+	int rc;
+
+	list_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
+		if (lsm != NULL && strcmp(lsm, hp->lsm))
+			continue;
+		rc = hp->hook.getprocattr(p, name, value);
+		if (rc != -ENOENT)
+			return rc;
+	}
+	return -EINVAL;
 }
 
-int security_setprocattr(const char *name, void *value, size_t size)
+int security_setprocattr(const char *lsm, const char *name, void *value,
+			 size_t size)
 {
-	return call_int_hook(setprocattr, -EINVAL, name, value, size);
+	struct security_hook_list *hp;
+	int rc;
+
+	list_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
+		if (lsm != NULL && strcmp(lsm, hp->lsm))
+			continue;
+		rc = hp->hook.setprocattr(name, value, size);
+		if (rc != -ENOENT)
+			return rc;
+	}
+	return -EINVAL;
 }
 
 int security_netlink_send(struct sock *sk, struct sk_buff *skb)
-- 
2.5.5

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#1661689 — [PATCH 6/6] LSM: general but not extreme module stacking

Subject: [PATCH 6/6] LSM: general but not extreme module stacking

Leverage the infrastructure management of the credential and
file security blobs to allow stacking of security modules in
all but the most extreme case. Security modules are informed
of the location of their data within the blobs at module
initialization.

Stacking is optional. If stacking is not configured the old
limit of one "major" security module applies. If stacking is
configured any combination that does not include both SELinux
and Smack is allowed.

A subdirectory has been added to /proc/.../attr for each of
SELinux and AppArmor (Smack introduced such a subdirectory earlier)
to disambiguate what data is provided in the proc/.../attr
interfaces. An entry "context" is added to /proc/.../attr and
to each of the subdirectories. The "context" entry provides
process attribute information in the form:

        lsm-name='lsm-data'[,lsm-name='lsm-data']...

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 Documentation/security/LSM.txt      |  18 ++++-
 fs/proc/base.c                      |  33 +++++++++
 include/linux/lsm_hooks.h           |   2 +-
 security/Kconfig                    |  94 ++++++++++++++++++++++++
 security/apparmor/include/context.h |  10 +++
 security/apparmor/lsm.c             |  43 +++++++++--
 security/security.c                 | 142 +++++++++++++++++++++++++++++++++++-
 security/selinux/hooks.c            |  24 +++++-
 security/selinux/include/objsec.h   |   8 ++
 security/smack/smack.h              |   9 +++
 security/smack/smack_lsm.c          |  23 +++---
 security/tomoyo/common.h            |  12 ++-
 security/tomoyo/tomoyo.c            |   3 +-
 13 files changed, 395 insertions(+), 26 deletions(-)

diff --git a/Documentation/security/LSM.txt b/Documentation/security/LSM.txt
index 57eafbc..23664b7 100644
--- a/Documentation/security/LSM.txt
+++ b/Documentation/security/LSM.txt
@@ -18,8 +18,14 @@ in the core functionality of Linux itself.
 
 The Linux capabilities modules will always be included. For more details
 on capabilities, see capabilities(7) in the Linux man-pages project.
-This may be followed by any number of "minor" modules and at most one
-"major" module.
+
+Security modules that do not use the security data blobs maintained
+by the LSM infrastructure are considered "minor" modules. These may be
+included at compile time and stacked explicitly. Security modules that
+use the LSM maintained security blobs are considered "major" modules.
+These may only be stacked if the CONFIG_LSM_STACKED configuration
+option is used. If this is chosen all of the security modules selected
+will be used.
 
 A list of the active security modules can be found by reading
 /sys/kernel/security/lsm. This is a comma separated list, and
@@ -36,6 +42,14 @@ security module and contains all its special files. The files directly
 in /proc/.../attr remain as legacy interfaces for modules that provide
 subdirectories.
 
+The files named "context" in the attr directories contain the
+same information as the "current" files, but formatted to
+identify the module it comes from.
+
+if selinux is the active security module:
+	/proc/self/attr/context could contain selinux='unconfined_t'
+	/proc/self/attr/selinux/context could contain selinux='unconfined_t'
+
 Based on https://lkml.org/lkml/2007/10/26/215,
 a new LSM is accepted into the kernel when its intent (a description of
 what it tries to protect against and in what cases one would expect to
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 10b777a..bfb1bf0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2549,13 +2549,37 @@ static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
 	.setattr	= proc_setattr, \
 }
 
+#ifdef CONFIG_SECURITY_SELINUX
+static const struct pid_entry selinux_attr_dir_stuff[] = {
+	ATTR("selinux", "current",	0666),
+	ATTR("selinux", "prev",		0444),
+	ATTR("selinux", "exec",		0666),
+	ATTR("selinux", "fscreate",	0666),
+	ATTR("selinux", "keycreate",	0666),
+	ATTR("selinux", "sockcreate",	0666),
+	ATTR("selinux", "context",	0666),
+};
+LSM_DIR_OPS(selinux);
+#endif
+
 #ifdef CONFIG_SECURITY_SMACK
 static const struct pid_entry smack_attr_dir_stuff[] = {
 	ATTR("smack", "current",	0666),
+	ATTR("smack", "context",	0666),
 };
 LSM_DIR_OPS(smack);
 #endif
 
+#ifdef CONFIG_SECURITY_APPARMOR
+static const struct pid_entry apparmor_attr_dir_stuff[] = {
+	ATTR("apparmor", "current",	0666),
+	ATTR("apparmor", "prev",	0444),
+	ATTR("apparmor", "exec",	0666),
+	ATTR("apparmor", "context",	0666),
+};
+LSM_DIR_OPS(apparmor);
+#endif
+
 static const struct pid_entry attr_dir_stuff[] = {
 	ATTR(NULL, "current",		0666),
 	ATTR(NULL, "prev",		0444),
@@ -2563,10 +2587,19 @@ static const struct pid_entry attr_dir_stuff[] = {
 	ATTR(NULL, "fscreate",		0666),
 	ATTR(NULL, "keycreate",		0666),
 	ATTR(NULL, "sockcreate",	0666),
+	ATTR(NULL, "context",		0666),
+#ifdef CONFIG_SECURITY_SELINUX
+	DIR("selinux",			0555,
+	    proc_selinux_attr_dir_inode_ops, proc_selinux_attr_dir_ops),
+#endif
 #ifdef CONFIG_SECURITY_SMACK
 	DIR("smack",			0555,
 	    proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
 #endif
+#ifdef CONFIG_SECURITY_APPARMOR
+	DIR("apparmor",			0555,
+	    proc_apparmor_attr_dir_inode_ops, proc_apparmor_attr_dir_ops),
+#endif
 };
 
 static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 0f30752..d514a63 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1950,7 +1950,7 @@ static inline void security_delete_hooks(struct security_hook_list *hooks,
 #define __lsm_ro_after_init	__ro_after_init
 #endif /* CONFIG_SECURITY_WRITABLE_HOOKS */
 
-extern int __init security_module_enable(const char *module);
+extern bool __init security_module_enable(const char *lsm, const bool stacked);
 extern void __init capability_add_hooks(void);
 #ifdef CONFIG_SECURITY_YAMA
 extern void __init yama_add_hooks(void);
diff --git a/security/Kconfig b/security/Kconfig
index 999509d8..4128619 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -36,6 +36,28 @@ config SECURITY_WRITABLE_HOOKS
 	bool
 	default n
 
+config SECURITY_STACKING
+	bool "Security module stacking"
+	depends on SECURITY
+	help
+	  Allows multiple major security modules to be stacked.
+	  Modules are invoked in the order registered with a
+	  "bail on fail" policy, in which the infrastructure
+	  will stop processing once a denial is detected. Not
+	  all modules can be stacked. SELinux and Smack are
+	  known to be incompatible. User space components may
+	  have trouble identifying the security module providing
+	  data in some cases.
+
+	  If you select this option you will have to select which
+	  of the stackable modules you wish to be active. The
+	  "Default security module" will be ignored. The boot line
+	  "security=" option can be used to specify that one of
+	  the modules identifed for stacking should be used instead
+	  of the entire stack.
+
+	  If you are unsure how to answer this question, answer N.
+
 config SECURITY_LSM_DEBUG
 	bool "Enable debugging of the LSM infrastructure"
 	depends on SECURITY
@@ -209,6 +231,9 @@ source security/yama/Kconfig
 
 source security/integrity/Kconfig
 
+menu "Security Module Selection"
+	visible if !SECURITY_STACKING
+
 choice
 	prompt "Default security module"
 	default DEFAULT_SECURITY_SELINUX if SECURITY_SELINUX
@@ -248,3 +273,72 @@ config DEFAULT_SECURITY
 
 endmenu
 
+menu "Security Module Stack"
+	visible if SECURITY_STACKING
+
+choice
+	prompt "Stacked 'extreme' security module"
+	default SECURITY_SELINUX_STACKED if SECURITY_SELINUX
+	default SECURITY_SMACK_STACKED if SECURITY_SMACK
+
+	help
+	  Enable an extreme security module. These modules cannot
+	  be used at the same time.
+
+	config SECURITY_SELINUX_STACKED
+		bool "SELinux" if SECURITY_SELINUX=y
+	help
+	  Add the SELinux security module to the stack. At this
+	  time the Smack security module is incompatible with this
+	  module.
+	  Please be sure your user space code is accomodating of
+	  this security module.
+
+	config SECURITY_SMACK_STACKED
+		bool "Simplified Mandatory Access Control" if SECURITY_SMACK=y
+	help
+	  Add the Smack security module to the stack. At this
+	  time the SELinux security module is incompatible with this
+	  module.
+	  Please be sure your user space code is accomodating of
+	  this security module.
+
+	config SECURITY_NOTHING_STACKED
+		bool "Use no 'extreme' security module"
+	help
+	  Add neither the SELinux security module nor the Smack security
+	  module to the stack.
+	  Please be sure your user space code does not require either of
+	  these security modules.
+
+endchoice
+
+config SECURITY_TOMOYO_STACKED
+	bool "TOMOYO support is enabled by default"
+	depends on SECURITY_TOMOYO && SECURITY_STACKING
+	default n
+	help
+	  This option instructs the system to use the TOMOYO checks.
+	  If not selected the module will not be invoked.
+	  Stacked security modules may interact in unexpected ways.
+	  Please be sure your user space code is accomodating of
+	  multiple security modules.
+
+	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_APPARMOR_STACKED
+	bool "AppArmor support is enabled by default"
+	depends on SECURITY_APPARMOR && SECURITY_STACKING
+	default n
+	help
+	  This option instructs the system to use the AppArmor checks.
+	  If not selected the module will not be invoked.
+	  Stacked security modules may interact in unexpected ways.
+	  Please be sure your user space code is accomodating of
+	  multiple security modules.
+
+	  If you are unsure how to answer this question, answer N.
+
+endmenu
+
+endmenu
diff --git a/security/apparmor/include/context.h b/security/apparmor/include/context.h
index 3ff3879..de3c4b8 100644
--- a/security/apparmor/include/context.h
+++ b/security/apparmor/include/context.h
@@ -88,14 +88,24 @@ int aa_set_current_hat(struct aa_profile *profile, u64 token);
 int aa_restore_previous_profile(u64 cookie);
 struct aa_profile *aa_get_task_profile(struct task_struct *task);
 
+extern struct lsm_blob_sizes apparmor_blob_sizes;
+
 static inline struct aa_task_ctx *apparmor_cred(const struct cred *cred)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return cred->security + apparmor_blob_sizes.lbs_cred;
+#else
 	return cred->security;
+#endif
 }
 
 static inline struct aa_file_ctx *apparmor_file(const struct file *file)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return file->f_security + apparmor_blob_sizes.lbs_file;
+#else
 	return file->f_security;
+#endif
 }
 
 /**
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 12a0265..32b8bb0 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -446,9 +446,13 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
 	const struct cred *cred = get_task_cred(task);
 	struct aa_task_ctx *ctx = cred_ctx(cred);
 	struct aa_profile *profile = NULL;
+	char *vp;
+	char *np;
 
 	if (strcmp(name, "current") == 0)
 		profile = aa_get_newest_profile(ctx->profile);
+	else if (strcmp(name, "context") == 0)
+		profile = aa_get_newest_profile(ctx->profile);
 	else if (strcmp(name, "prev") == 0  && ctx->previous)
 		profile = aa_get_newest_profile(ctx->previous);
 	else if (strcmp(name, "exec") == 0 && ctx->onexec)
@@ -456,9 +460,29 @@ static int apparmor_getprocattr(struct task_struct *task, char *name,
 	else
 		error = -EINVAL;
 
-	if (profile)
-		error = aa_getprocattr(profile, value);
+	if (profile == NULL)
+		goto put_out;
+
+	error = aa_getprocattr(profile, &vp);
+	if (error < 0)
+		goto put_out;
+
+	if (strcmp(name, "context") == 0) {
+		*value = kasprintf(GFP_KERNEL, "apparmor='%s'", vp);
+		if (*value == NULL) {
+			error = -ENOMEM;
+			goto put_out;
+		}
+		np = strchr(*value, '\n');
+		if (np != NULL) {
+			np[0] = '\'';
+			np[1] = '\0';
+		}
+		error = strlen(*value);
+	} else
+		*value = vp;
 
+put_out:
 	aa_put_profile(profile);
 	put_cred(cred);
 
@@ -496,7 +520,7 @@ static int apparmor_setprocattr(const char *name, void *value,
 		goto out;
 
 	arg_size = size - (args - (largs ? largs : (char *) value));
-	if (strcmp(name, "current") == 0) {
+	if (strcmp(name, "current") == 0 || strcmp(name, "context") == 0) {
 		if (strcmp(command, "changehat") == 0) {
 			error = aa_setprocattr_changehat(args, arg_size,
 							 !AA_DO_TEST);
@@ -518,7 +542,10 @@ static int apparmor_setprocattr(const char *name, void *value,
 		else
 			goto fail;
 	} else
-		/* only support the "current" and "exec" process attributes */
+		/*
+		 * only support the "current", "context" and "exec"
+		 * process attributes
+		 */
 		goto fail;
 
 	if (!error)
@@ -918,13 +945,17 @@ static int __init apparmor_init(void)
 	int error;
 
 	if (!finish) {
-		if (apparmor_enabled && security_module_enable("apparmor"))
+		if (apparmor_enabled &&
+		    security_module_enable("apparmor",
+				IS_ENABLED(CONFIG_SECURITY_APPARMOR_STACKED)))
 			security_add_blobs(&apparmor_blob_sizes);
 		finish = 1;
 		return 0;
 	}
 
-	if (!apparmor_enabled || !security_module_enable("apparmor")) {
+	if (!apparmor_enabled ||
+	    !security_module_enable("apparmor",
+				IS_ENABLED(CONFIG_SECURITY_APPARMOR_STACKED))) {
 		aa_info_message("AppArmor disabled by boot time parameter");
 		apparmor_enabled = 0;
 		return 0;
diff --git a/security/security.c b/security/security.c
index 1004914..895e9ef 100644
--- a/security/security.c
+++ b/security/security.c
@@ -34,6 +34,7 @@
 
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
+#define MODULE_STACK		"(stacking)"
 
 struct security_hook_heads security_hook_heads __lsm_ro_after_init;
 char *lsm_names;
@@ -41,7 +42,11 @@ static struct lsm_blob_sizes blob_sizes;
 
 /* Boot-time LSM user choice */
 static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
+#ifdef CONFIG_SECURITY_STACKING
+	MODULE_STACK;
+#else
 	CONFIG_DEFAULT_SECURITY;
+#endif
 
 static void __init do_security_initcalls(void)
 {
@@ -150,6 +155,7 @@ static int lsm_append(char *new, char **result)
 /**
  * security_module_enable - Load given security module on boot ?
  * @module: the name of the module
+ * @stacked: indicates that the module wants to be stacked
  *
  * Each LSM must pass this method before registering its own operations
  * to avoid security registration races. This method may also be used
@@ -165,9 +171,29 @@ static int lsm_append(char *new, char **result)
  *
  * Otherwise, return false.
  */
-int __init security_module_enable(const char *module)
+bool __init security_module_enable(const char *lsm, const bool stacked)
 {
-	return !strcmp(module, chosen_lsm);
+#ifdef CONFIG_SECURITY_STACKING
+	/*
+	 * Module defined on the command line security=XXXX
+	 */
+	if (strcmp(chosen_lsm, MODULE_STACK)) {
+		if (!strcmp(lsm, chosen_lsm)) {
+			pr_info("Command line sets the %s security module.\n",
+				lsm);
+			return true;
+		}
+		return false;
+	}
+	/*
+	 * Module configured as stacked.
+	 */
+	return stacked;
+#else
+	if (strcmp(lsm, chosen_lsm) == 0)
+		return true;
+	return false;
+#endif
 }
 
 /**
@@ -1642,8 +1668,49 @@ int security_getprocattr(struct task_struct *p, const char *lsm, char *name,
 				char **value)
 {
 	struct security_hook_list *hp;
+	char *vp;
+	char *cp = NULL;
+	int trc;
 	int rc;
 
+	/*
+	 * "context" requires work here in addition to what
+	 * the modules provide.
+	 */
+	if (strcmp(name, "context") == 0) {
+		*value = NULL;
+		rc = -EINVAL;
+		list_for_each_entry(hp,
+				&security_hook_heads.getprocattr, list) {
+			if (lsm != NULL && strcmp(lsm, hp->lsm))
+				continue;
+			trc = hp->hook.getprocattr(p, "context", &vp);
+			if (trc == -ENOENT)
+				continue;
+			if (trc <= 0) {
+				kfree(*value);
+				return trc;
+			}
+			rc = trc;
+			if (*value == NULL) {
+				*value = vp;
+			} else {
+				cp = kasprintf(GFP_KERNEL, "%s,%s", *value, vp);
+				if (cp == NULL) {
+					kfree(*value);
+					kfree(vp);
+					return -ENOMEM;
+				}
+				kfree(*value);
+				kfree(vp);
+				*value = cp;
+			}
+		}
+		if (rc > 0)
+			return strlen(*value);
+		return rc;
+	}
+
 	list_for_each_entry(hp, &security_hook_heads.getprocattr, list) {
 		if (lsm != NULL && strcmp(lsm, hp->lsm))
 			continue;
@@ -1659,6 +1726,77 @@ int security_setprocattr(const char *lsm, const char *name, void *value,
 {
 	struct security_hook_list *hp;
 	int rc;
+	char *local;
+	char *cp;
+	int slen;
+	int failed = 0;
+
+	/*
+	 * If lsm is NULL look at all the modules to find one
+	 * that processes name. If lsm is not NULL only look at
+	 * that module.
+	 *
+	 * "context" is handled directly here.
+	 */
+	if (strcmp(name, "context") == 0) {
+		/*
+		 * First verify that the input is acceptable.
+		 * lsm1='v1'lsm2='v2'lsm3='v3'
+		 *
+		 * A note on the use of strncmp() below.
+		 * The check is for the substring at the beginning of cp.
+		 * The kzalloc of size + 1 ensures a terminated string.
+		 */
+		rc = -EINVAL;
+		local = kzalloc(size + 1, GFP_KERNEL);
+		memcpy(local, value, size);
+		cp = local;
+		list_for_each_entry(hp, &security_hook_heads.setprocattr,
+					list) {
+			if (lsm != NULL && strcmp(lsm, hp->lsm))
+				continue;
+			if (cp[0] == ',') {
+				if (cp == local)
+					goto free_out;
+				cp++;
+			}
+			slen = strlen(hp->lsm);
+			if (strncmp(cp, hp->lsm, slen))
+				goto free_out;
+			cp += slen;
+			if (cp[0] != '=' || cp[1] != '\'' || cp[2] == '\'')
+				goto free_out;
+			for (cp += 2; cp[0] != '\''; cp++)
+				if (cp[0] == '\0')
+					goto free_out;
+			cp++;
+		}
+
+		cp = local;
+		list_for_each_entry(hp, &security_hook_heads.setprocattr,
+					list) {
+			if (lsm != NULL && strcmp(lsm, hp->lsm))
+				continue;
+			if (cp[0] == ',')
+				cp++;
+			cp += strlen(hp->lsm) + 2;
+			for (slen = 0; cp[slen] != '\''; slen++)
+				;
+			cp[slen] = '\0';
+
+			rc = hp->hook.setprocattr("context", cp, slen);
+			if (rc < 0)
+				failed = rc;
+			cp += slen + 1;
+		}
+		if (failed != 0)
+			rc = failed;
+		else
+			rc = size;
+free_out:
+		kfree(local);
+		return rc;
+	}
 
 	list_for_each_entry(hp, &security_hook_heads.setprocattr, list) {
 		if (lsm != NULL && strcmp(lsm, hp->lsm))
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 6e51ae5..cc8c177 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5682,6 +5682,8 @@ static int selinux_getprocattr(struct task_struct *p,
 
 	if (!strcmp(name, "current"))
 		sid = __tsec->sid;
+	else if (!strcmp(name, "context"))
+		sid = __tsec->sid;
 	else if (!strcmp(name, "prev"))
 		sid = __tsec->osid;
 	else if (!strcmp(name, "exec"))
@@ -5701,7 +5703,19 @@ static int selinux_getprocattr(struct task_struct *p,
 	if (!sid)
 		return 0;
 
-	error = security_sid_to_context(sid, value, &len);
+	if (strcmp(name, "context")) {
+		error = security_sid_to_context(sid, value, &len);
+	} else {
+		char *vp;
+
+		error = security_sid_to_context(sid, &vp, &len);
+		if (!error) {
+			*value = kasprintf(GFP_KERNEL, "selinux='%s'", vp);
+			if (*value == NULL)
+				error = -ENOMEM;
+		}
+	}
+
 	if (error)
 		return error;
 	return len;
@@ -5737,6 +5751,9 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 	else if (!strcmp(name, "current"))
 		error = avc_has_perm(mysid, mysid, SECCLASS_PROCESS,
 				     PROCESS__SETCURRENT, NULL);
+	else if (!strcmp(name, "context"))
+		error = avc_has_perm(mysid, mysid, SECCLASS_PROCESS,
+				     PROCESS__SETCURRENT, NULL);
 	else
 		error = -EINVAL;
 	if (error)
@@ -5797,7 +5814,7 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
 		tsec->keycreate_sid = sid;
 	} else if (!strcmp(name, "sockcreate")) {
 		tsec->sockcreate_sid = sid;
-	} else if (!strcmp(name, "current")) {
+	} else if (!strcmp(name, "current") || !strcmp(name, "context")) {
 		error = -EINVAL;
 		if (sid == 0)
 			goto abort_change;
@@ -6174,7 +6191,8 @@ static __init int selinux_init(void)
 {
 	static int finish;
 
-	if (!security_module_enable("selinux")) {
+	if (!security_module_enable("selinux",
+				IS_ENABLED(CONFIG_SECURITY_SELINUX_STACKED))) {
 		selinux_enabled = 0;
 		return 0;
 	}
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index 1b1dff4..05fe04a 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -144,12 +144,20 @@ extern struct lsm_blob_sizes selinux_blob_sizes;
 
 static inline struct task_security_struct *selinux_cred(const struct cred *cred)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return cred->security + selinux_blob_sizes.lbs_cred;
+#else
 	return cred->security;
+#endif
 }
 
 static inline struct file_security_struct *selinux_file(const struct file *file)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return file->f_security + selinux_blob_sizes.lbs_file;
+#else
 	return file->f_security;
+#endif
 }
 
 static inline struct inode_security_struct *selinux_inode(
diff --git a/security/smack/smack.h b/security/smack/smack.h
index f4ad92d..e1cd53e 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -336,6 +336,7 @@ extern struct smack_known *smack_syslog_label;
 extern struct smack_known *smack_unconfined;
 #endif
 extern int smack_ptrace_rule;
+extern struct lsm_blob_sizes smack_blob_sizes;
 
 extern struct smack_known smack_known_floor;
 extern struct smack_known smack_known_hat;
@@ -358,12 +359,20 @@ extern struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
 
 static inline struct task_smack *smack_cred(const struct cred *cred)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return cred->security + smack_blob_sizes.lbs_cred;
+#else
 	return cred->security;
+#endif
 }
 
 static inline struct smack_known **smack_file(const struct file *file)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return file->f_security + smack_blob_sizes.lbs_file;
+#else
 	return file->f_security;
+#endif
 }
 
 static inline struct inode_smack *smack_inode(const struct inode *inode)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index a0b580e..b2589eb 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3453,18 +3453,20 @@ static int smack_getprocattr(struct task_struct *p, char *name, char **value)
 {
 	struct smack_known *skp = smk_of_task_struct(p);
 	char *cp;
-	int slen;
 
-	if (strcmp(name, "current") != 0)
+	if (strcmp(name, "current") == 0) {
+		cp = kstrdup(skp->smk_known, GFP_KERNEL);
+		if (cp == NULL)
+			return -ENOMEM;
+	} else if (strcmp(name, "context") == 0) {
+		cp = kasprintf(GFP_KERNEL, "smack='%s'", skp->smk_known);
+		if (cp == NULL)
+			return -ENOMEM;
+	} else
 		return -EINVAL;
 
-	cp = kstrdup(skp->smk_known, GFP_KERNEL);
-	if (cp == NULL)
-		return -ENOMEM;
-
-	slen = strlen(cp);
 	*value = cp;
-	return slen;
+	return strlen(cp);
 }
 
 /**
@@ -3492,7 +3494,7 @@ static int smack_setprocattr(const char *name, void *value, size_t size)
 	if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
 		return -EINVAL;
 
-	if (strcmp(name, "current") != 0)
+	if (strcmp(name, "current") != 0 && strcmp(name, "context") != 0)
 		return -EINVAL;
 
 	skp = smk_import_entry(value, size);
@@ -4622,7 +4624,8 @@ static __init int smack_init(void)
 	struct cred *cred = (struct cred *) current->cred;
 	struct task_smack *tsp;
 
-	if (!security_module_enable("smack"))
+	if (!security_module_enable("smack",
+				IS_ENABLED(CONFIG_SECURITY_SMACK_STACKED)))
 		return 0;
 
 	if (!finish) {
diff --git a/security/tomoyo/common.h b/security/tomoyo/common.h
index cbcfccc..2eed9d4 100644
--- a/security/tomoyo/common.h
+++ b/security/tomoyo/common.h
@@ -1085,6 +1085,7 @@ extern struct tomoyo_domain_info tomoyo_kernel_domain;
 extern struct tomoyo_policy_namespace tomoyo_kernel_namespace;
 extern unsigned int tomoyo_memory_quota[TOMOYO_MAX_MEMORY_STAT];
 extern unsigned int tomoyo_memory_used[TOMOYO_MAX_MEMORY_STAT];
+extern struct lsm_blob_sizes tomoyo_blob_sizes;
 
 /********** Inlined functions. **********/
 
@@ -1204,7 +1205,11 @@ static inline void tomoyo_put_group(struct tomoyo_group *group)
  */
 static inline struct tomoyo_domain_info **tomoyo_cred(const struct cred *cred)
 {
+#ifdef CONFIG_SECURITY_STACKING
+	return cred->security + tomoyo_blob_sizes.lbs_cred;
+#else
 	return cred->security;
+#endif
 }
 
 /**
@@ -1214,8 +1219,13 @@ static inline struct tomoyo_domain_info **tomoyo_cred(const struct cred *cred)
  */
 static inline struct tomoyo_domain_info *tomoyo_domain(void)
 {
-	struct tomoyo_domain_info **blob = tomoyo_cred(current_cred());
+	const struct cred *cred = current_cred();
+	struct tomoyo_domain_info **blob;
+
+	if (cred->security == NULL)
+		return NULL;
 
+	blob = tomoyo_cred(cred);
 	return *blob;
 }
 
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index 901fa78..aa52fff 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -561,7 +561,8 @@ static int __init tomoyo_init(void)
 	struct cred *cred = (struct cred *) current_cred();
 	struct tomoyo_domain_info **blob;
 
-	if (!security_module_enable("tomoyo"))
+	if (!security_module_enable("tomoyo",
+				IS_ENABLED(CONFIG_SECURITY_TOMOYO_STACKED)))
 		return 0;
 
 	if (!finish) {
-- 
2.5.5

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#1661691 — Re: [kernel-hardening] [PATCH 0/6] LSM: Security module blob management

On 6/8/17 4:43 PM, Casey Schaufler wrote:
> Subject: [PATCH 0/6] LSM: Security module blob management
> 
> This patch set moves management of security blobs out of
> the Linux security modules and into the security module
> infrastructure. This allows "major" security modules that
> use blobs to be stacked, just as "minor" modules that
> do not use blobs can be stacked today. It stops short of
> providing a safe interface for the Netlabel and SO_PEERSEC.
> As a result, any of the existing security modules may be
> used in combination except for SELinux and Smack.

Very excited about this! I can definitely see use cases for special
purpose LSMs that require data blobs but do not replace things like
SELinux, SMACK or AppArmor. I have had a few ideas recently that would
not be possible under the current setup of one shared blob.

Matt

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#1661902 — Re: [kernel-hardening] [PATCH 0/6] LSM: Security module blob management

On Thu, 8 Jun 2017, Matt Brown wrote:

> On 6/8/17 4:43 PM, Casey Schaufler wrote:
> > Subject: [PATCH 0/6] LSM: Security module blob management
> > 
> > This patch set moves management of security blobs out of
> > the Linux security modules and into the security module
> > infrastructure. This allows "major" security modules that
> > use blobs to be stacked, just as "minor" modules that
> > do not use blobs can be stacked today. It stops short of
> > providing a safe interface for the Netlabel and SO_PEERSEC.
> > As a result, any of the existing security modules may be
> > used in combination except for SELinux and Smack.
> 
> Very excited about this! I can definitely see use cases for special
> purpose LSMs that require data blobs but do not replace things like
> SELinux, SMACK or AppArmor. I have had a few ideas recently that would
> not be possible under the current setup of one shared blob.

Please post details of these ideas once you have say a prototype working 
with Casey's patches.


-- 
James Morris
<jmorris@namei.org>

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