Merge v6.18.38linux-rolling-lts

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

11 files changed, 399 insertions, 76 deletions

diff --git a/security/apparmor/include/policy_unpack.h b/security/apparmor/include/policy_unpack.h
index e5a95dc4da1f..b9de0fdf9ee5 100644
--- a/security/apparmor/include/policy_unpack.h
+++ b/security/apparmor/include/policy_unpack.h
@@ -163,6 +163,25 @@ aa_get_profile_loaddata(struct aa_loaddata *data)
 	return data;
 }
 
+/**
+ * aa_get_profile_loaddata_not0 - get a profile reference count if not zero
+ * @data: reference to get a count on
+ *
+ * Like aa_get_profile_loaddata(), but safe to call on an entry that may
+ * be on a list (e.g. ns->rawdata_list) where the last pcount has already
+ * dropped and the deferred cleanup has not yet run.
+ *
+ * Returns: pointer to reference, or %NULL if @data is NULL or its
+ *          profile refcount has already reached zero.
+ */
+static inline struct aa_loaddata *
+aa_get_profile_loaddata_not0(struct aa_loaddata *data)
+{
+	if (data && kref_get_unless_zero(&data->pcount))
+		return data;
+	return NULL;
+}
+
 void __aa_loaddata_update(struct aa_loaddata *data, long revision);
 bool aa_rawdata_eq(struct aa_loaddata *l, struct aa_loaddata *r);
 void aa_loaddata_kref(struct kref *kref);
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 3a4ef7bd3b5d..e47696a7eacf 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -1423,7 +1423,21 @@ static int aa_sock_msg_perm(const char *op, u32 request, struct socket *sock,
 static int apparmor_socket_sendmsg(struct socket *sock,
 				   struct msghdr *msg, int size)
 {
-	return aa_sock_msg_perm(OP_SENDMSG, AA_MAY_SEND, sock, msg, size);
+	int error = aa_sock_msg_perm(OP_SENDMSG, AA_MAY_SEND, sock, msg, size);
+
+	if (error)
+		return error;
+
+	/* TCP fast open carries connect() semantics in sendmsg(); mediate
+	 * the implicit connect so it cannot bypass the connect permission.
+	 */
+	if ((msg->msg_flags & MSG_FASTOPEN) && msg->msg_name &&
+	    (sk_is_tcp(sock->sk) ||
+	     (sk_is_inet(sock->sk) && sock->sk->sk_type == SOCK_STREAM &&
+	      sock->sk->sk_protocol == IPPROTO_MPTCP)))
+		error = aa_sk_perm(OP_CONNECT, AA_MAY_CONNECT, sock->sk);
+
+	return error;
 }
 
 static int apparmor_socket_recvmsg(struct socket *sock,
diff --git a/security/apparmor/net.c b/security/apparmor/net.c
index 44c04102062f..1fc6145ccbb8 100644
--- a/security/apparmor/net.c
+++ b/security/apparmor/net.c
@@ -22,12 +22,14 @@
 
 struct aa_sfs_entry aa_sfs_entry_network[] = {
 	AA_SFS_FILE_STRING("af_mask",	AA_SFS_AF_MASK),
+	AA_SFS_FILE_BOOLEAN("tcp-fast-open",		1),
 	{ }
 };
 
 struct aa_sfs_entry aa_sfs_entry_networkv9[] = {
 	AA_SFS_FILE_STRING("af_mask",	AA_SFS_AF_MASK),
 	AA_SFS_FILE_BOOLEAN("af_unix",	1),
+	AA_SFS_FILE_BOOLEAN("tcp-fast-open",		1),
 	{ }
 };
 
diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c
index b92db1b2f26e..c474a55fed22 100644
--- a/security/apparmor/policy.c
+++ b/security/apparmor/policy.c
@@ -1206,8 +1206,12 @@ ssize_t aa_replace_profiles(struct aa_ns *policy_ns, struct aa_label *label,
 			if (aa_rawdata_eq(rawdata_ent, udata)) {
 				struct aa_loaddata *tmp;
 
-				tmp = aa_get_profile_loaddata(rawdata_ent);
-				/* check we didn't fail the race */
+				/*
+				 * Entries remain on rawdata_list with
+				 * pcount == 0 until do_ploaddata_rmfs()
+				 * runs; only take a live profile ref.
+				 */
+				tmp = aa_get_profile_loaddata_not0(rawdata_ent);
 				if (tmp) {
 					aa_put_profile_loaddata(udata);
 					udata = tmp;
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 2cffa6dc8255..b7b622bc36a1 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -208,6 +208,8 @@ extern struct key *request_key_auth_new(struct key *target,
 					const void *callout_info,
 					size_t callout_len,
 					struct key *dest_keyring);
+struct request_key_auth *request_key_auth_get(struct key *authkey);
+void request_key_auth_put(struct request_key_auth *rka);
 
 extern struct key *key_get_instantiation_authkey(key_serial_t target_id);
 
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index ab927a142f51..11bedca4e1c6 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1197,9 +1197,13 @@ static long keyctl_instantiate_key_common(key_serial_t id,
 	if (!instkey)
 		goto error;
 
-	rka = instkey->payload.data[0];
-	if (rka->target_key->serial != id)
+	rka = request_key_auth_get(instkey);
+	if (!rka) {
+		ret = -EKEYREVOKED;
 		goto error;
+	}
+	if (rka->target_key->serial != id)
+		goto error_put_rka;
 
 	/* pull the payload in if one was supplied */
 	payload = NULL;
@@ -1208,7 +1212,7 @@ static long keyctl_instantiate_key_common(key_serial_t id,
 		ret = -ENOMEM;
 		payload = kvmalloc(plen, GFP_KERNEL);
 		if (!payload)
-			goto error;
+			goto error_put_rka;
 
 		ret = -EFAULT;
 		if (!copy_from_iter_full(payload, plen, from))
@@ -1234,6 +1238,8 @@ static long keyctl_instantiate_key_common(key_serial_t id,
 
 error2:
 	kvfree_sensitive(payload, plen);
+error_put_rka:
+	request_key_auth_put(rka);
 error:
 	return ret;
 }
@@ -1358,15 +1364,19 @@ long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
 	if (!instkey)
 		goto error;
 
-	rka = instkey->payload.data[0];
-	if (rka->target_key->serial != id)
+	rka = request_key_auth_get(instkey);
+	if (!rka) {
+		ret = -EKEYREVOKED;
 		goto error;
+	}
+	if (rka->target_key->serial != id)
+		goto error_put_rka;
 
 	/* find the destination keyring if present (which must also be
 	 * writable) */
 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
 	if (ret < 0)
-		goto error;
+		goto error_put_rka;
 
 	/* instantiate the key and link it into a keyring */
 	ret = key_reject_and_link(rka->target_key, timeout, error,
@@ -1379,6 +1389,8 @@ long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
 	if (ret == 0)
 		keyctl_change_reqkey_auth(NULL);
 
+error_put_rka:
+	request_key_auth_put(rka);
 error:
 	return ret;
 }
diff --git a/security/keys/keyctl_pkey.c b/security/keys/keyctl_pkey.c
index 97bc27bbf079..ba150ee2d4a3 100644
--- a/security/keys/keyctl_pkey.c
+++ b/security/keys/keyctl_pkey.c
@@ -138,28 +138,35 @@ static int keyctl_pkey_params_get_2(const struct keyctl_pkey_params __user *_par
 		if (uparams.in_len  > info.max_dec_size ||
 		    uparams.out_len > info.max_enc_size)
 			return -EINVAL;
+
+		params->out_len = info.max_enc_size;
 		break;
 	case KEYCTL_PKEY_DECRYPT:
 		if (uparams.in_len  > info.max_enc_size ||
 		    uparams.out_len > info.max_dec_size)
 			return -EINVAL;
+
+		params->out_len = info.max_dec_size;
 		break;
 	case KEYCTL_PKEY_SIGN:
 		if (uparams.in_len  > info.max_data_size ||
 		    uparams.out_len > info.max_sig_size)
 			return -EINVAL;
+
+		params->out_len = info.max_sig_size;
 		break;
 	case KEYCTL_PKEY_VERIFY:
 		if (uparams.in_len  > info.max_data_size ||
 		    uparams.in2_len > info.max_sig_size)
 			return -EINVAL;
+
+		params->out_len = info.max_sig_size;
 		break;
 	default:
 		BUG();
 	}
 
 	params->in_len  = uparams.in_len;
-	params->out_len = uparams.out_len; /* Note: same as in2_len */
 	return 0;
 }
 
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
index 8f33cd170e42..bd34317b58cc 100644
--- a/security/keys/request_key_auth.c
+++ b/security/keys/request_key_auth.c
@@ -23,6 +23,7 @@ static void request_key_auth_describe(const struct key *, struct seq_file *);
 static void request_key_auth_revoke(struct key *);
 static void request_key_auth_destroy(struct key *);
 static long request_key_auth_read(const struct key *, char *, size_t);
+static void request_key_auth_rcu_disposal(struct rcu_head *);
 
 /*
  * The request-key authorisation key type definition.
@@ -116,6 +117,31 @@ static void free_request_key_auth(struct request_key_auth *rka)
 }
 
 /*
+ * Take a reference to the request-key authorisation payload so callers can
+ * drop authkey->sem before doing operations that may sleep.
+ */
+struct request_key_auth *request_key_auth_get(struct key *authkey)
+{
+	struct request_key_auth *rka;
+
+	down_read(&authkey->sem);
+	rka = dereference_key_locked(authkey);
+	if (rka && !test_bit(KEY_FLAG_REVOKED, &authkey->flags))
+		refcount_inc(&rka->usage);
+	else
+		rka = NULL;
+	up_read(&authkey->sem);
+
+	return rka;
+}
+
+void request_key_auth_put(struct request_key_auth *rka)
+{
+	if (rka && refcount_dec_and_test(&rka->usage))
+		call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
+}
+
+/*
  * Dispose of the request_key_auth record under RCU conditions
  */
 static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
@@ -136,8 +162,10 @@ static void request_key_auth_revoke(struct key *key)
 	struct request_key_auth *rka = dereference_key_locked(key);
 
 	kenter("{%d}", key->serial);
+	if (!rka)
+		return;
 	rcu_assign_keypointer(key, NULL);
-	call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
+	request_key_auth_put(rka);
 }
 
 /*
@@ -150,7 +178,7 @@ static void request_key_auth_destroy(struct key *key)
 	kenter("{%d}", key->serial);
 	if (rka) {
 		rcu_assign_keypointer(key, NULL);
-		call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
+		request_key_auth_put(rka);
 	}
 }
 
@@ -174,6 +202,7 @@ struct key *request_key_auth_new(struct key *target, const char *op,
 	rka = kzalloc(sizeof(*rka), GFP_KERNEL);
 	if (!rka)
 		goto error;
+	refcount_set(&rka->usage, 1);
 	rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
 	if (!rka->callout_info)
 		goto error_free_rka;
diff --git a/security/security.c b/security/security.c
index 603c3c6d5635..9285909908ab 100644
--- a/security/security.c
+++ b/security/security.c
@@ -94,6 +94,7 @@ const char *const lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX + 1] = {
 static BLOCKING_NOTIFIER_HEAD(blocking_lsm_notifier_chain);
 
 static struct kmem_cache *lsm_file_cache;
+static struct kmem_cache *lsm_backing_file_cache;
 static struct kmem_cache *lsm_inode_cache;
 
 char *lsm_names;
@@ -265,6 +266,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
 
 	lsm_set_blob_size(&needed->lbs_cred, &blob_sizes.lbs_cred);
 	lsm_set_blob_size(&needed->lbs_file, &blob_sizes.lbs_file);
+	lsm_set_blob_size(&needed->lbs_backing_file, &blob_sizes.lbs_backing_file);
 	lsm_set_blob_size(&needed->lbs_ib, &blob_sizes.lbs_ib);
 	/*
 	 * The inode blob gets an rcu_head in addition to
@@ -470,6 +472,7 @@ static void __init ordered_lsm_init(void)
 
 	init_debug("cred blob size       = %d\n", blob_sizes.lbs_cred);
 	init_debug("file blob size       = %d\n", blob_sizes.lbs_file);
+	init_debug("lsm_backing_file_cache	 = %d\n", blob_sizes.lbs_backing_file);
 	init_debug("ib blob size         = %d\n", blob_sizes.lbs_ib);
 	init_debug("inode blob size      = %d\n", blob_sizes.lbs_inode);
 	init_debug("ipc blob size        = %d\n", blob_sizes.lbs_ipc);
@@ -495,6 +498,11 @@ static void __init ordered_lsm_init(void)
 		lsm_file_cache = kmem_cache_create("lsm_file_cache",
 						   blob_sizes.lbs_file, 0,
 						   SLAB_PANIC, NULL);
+	if (blob_sizes.lbs_backing_file)
+		lsm_backing_file_cache = kmem_cache_create(
+						   "lsm_backing_file_cache",
+						   blob_sizes.lbs_backing_file,
+						   0, SLAB_PANIC, NULL);
 	if (blob_sizes.lbs_inode)
 		lsm_inode_cache = kmem_cache_create("lsm_inode_cache",
 						    blob_sizes.lbs_inode, 0,
@@ -672,6 +680,30 @@ int unregister_blocking_lsm_notifier(struct notifier_block *nb)
 EXPORT_SYMBOL(unregister_blocking_lsm_notifier);
 
 /**
+ * lsm_backing_file_alloc - allocate a composite backing file blob
+ * @backing_file: the backing file
+ *
+ * Allocate the backing file blob for all the modules.
+ *
+ * Returns 0, or -ENOMEM if memory can't be allocated.
+ */
+static int lsm_backing_file_alloc(struct file *backing_file)
+{
+	void *blob;
+
+	if (!lsm_backing_file_cache) {
+		backing_file_set_security(backing_file, NULL);
+		return 0;
+	}
+
+	blob = kmem_cache_zalloc(lsm_backing_file_cache, GFP_KERNEL);
+	backing_file_set_security(backing_file, blob);
+	if (!blob)
+		return -ENOMEM;
+	return 0;
+}
+
+/**
  * lsm_blob_alloc - allocate a composite blob
  * @dest: the destination for the blob
  * @size: the size of the blob
@@ -2966,6 +2998,57 @@ void security_file_free(struct file *file)
 }
 
 /**
+ * security_backing_file_alloc() - Allocate and setup a backing file blob
+ * @backing_file: the backing file
+ * @user_file: the associated user visible file
+ *
+ * Allocate a backing file LSM blob and perform any necessary initialization of
+ * the LSM blob.  There will be some operations where the LSM will not have
+ * access to @user_file after this point, so any important state associated
+ * with @user_file that is important to the LSM should be captured in the
+ * backing file's LSM blob.
+ *
+ * LSM's should avoid taking a reference to @user_file in this hook as it will
+ * result in problems later when the system attempts to drop/put the file
+ * references due to a circular dependency.
+ *
+ * Return: Return 0 if the hook is successful, negative values otherwise.
+ */
+int security_backing_file_alloc(struct file *backing_file,
+				const struct file *user_file)
+{
+	int rc;
+
+	rc = lsm_backing_file_alloc(backing_file);
+	if (rc)
+		return rc;
+	rc = call_int_hook(backing_file_alloc, backing_file, user_file);
+	if (unlikely(rc))
+		security_backing_file_free(backing_file);
+
+	return rc;
+}
+
+/**
+ * security_backing_file_free() - Free a backing file blob
+ * @backing_file: the backing file
+ *
+ * Free any LSM state associate with a backing file's LSM blob, including the
+ * blob itself.
+ */
+void security_backing_file_free(struct file *backing_file)
+{
+	void *blob = backing_file_security(backing_file);
+
+	call_void_hook(backing_file_free, backing_file);
+
+	if (blob) {
+		backing_file_set_security(backing_file, NULL);
+		kmem_cache_free(lsm_backing_file_cache, blob);
+	}
+}
+
+/**
  * security_file_ioctl() - Check if an ioctl is allowed
  * @file: associated file
  * @cmd: ioctl cmd
@@ -3054,6 +3137,32 @@ int security_mmap_file(struct file *file, unsigned long prot,
 }
 
 /**
+ * security_mmap_backing_file - Check if mmap'ing a backing file is allowed
+ * @vma: the vm_area_struct for the mmap'd region
+ * @backing_file: the backing file being mmap'd
+ * @user_file: the user file being mmap'd
+ *
+ * Check permissions for a mmap operation on a stacked filesystem.  This hook
+ * is called after the security_mmap_file() and is responsible for authorizing
+ * the mmap on @backing_file.  It is important to note that the mmap operation
+ * on @user_file has already been authorized and the @vma->vm_file has been
+ * set to @backing_file.
+ *
+ * Return: Returns 0 if permission is granted.
+ */
+int security_mmap_backing_file(struct vm_area_struct *vma,
+			       struct file *backing_file,
+			       struct file *user_file)
+{
+	/* recommended by the stackable filesystem devs */
+	if (WARN_ON_ONCE(!(backing_file->f_mode & FMODE_BACKING)))
+		return -EIO;
+
+	return call_int_hook(mmap_backing_file, vma, backing_file, user_file);
+}
+EXPORT_SYMBOL_GPL(security_mmap_backing_file);
+
+/**
  * security_mmap_addr() - Check if mmap'ing an address is allowed
  * @addr: address
  *
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3da3017ad2ca..f96ee8f372e3 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1739,49 +1739,72 @@ static inline int file_path_has_perm(const struct cred *cred,
 static int bpf_fd_pass(const struct file *file, u32 sid);
 #endif
 
-/* Check whether a task can use an open file descriptor to
-   access an inode in a given way.  Check access to the
-   descriptor itself, and then use dentry_has_perm to
-   check a particular permission to the file.
-   Access to the descriptor is implicitly granted if it
-   has the same SID as the process.  If av is zero, then
-   access to the file is not checked, e.g. for cases
-   where only the descriptor is affected like seek. */
-static int file_has_perm(const struct cred *cred,
-			 struct file *file,
-			 u32 av)
+static int __file_has_perm(const struct cred *cred, const struct file *file,
+			   u32 av, bool bf_user_file)
+
 {
-	struct file_security_struct *fsec = selinux_file(file);
-	struct inode *inode = file_inode(file);
 	struct common_audit_data ad;
-	u32 sid = cred_sid(cred);
+	struct inode *inode;
+	u32 ssid = cred_sid(cred);
+	u32 tsid_fd;
 	int rc;
 
-	ad.type = LSM_AUDIT_DATA_FILE;
-	ad.u.file = file;
+	if (bf_user_file) {
+		struct backing_file_security_struct *bfsec;
+		const struct path *path;
 
-	if (sid != fsec->sid) {
-		rc = avc_has_perm(sid, fsec->sid,
-				  SECCLASS_FD,
-				  FD__USE,
-				  &ad);
+		if (WARN_ON(!(file->f_mode & FMODE_BACKING)))
+			return -EIO;
+
+		bfsec = selinux_backing_file(file);
+		path = backing_file_user_path(file);
+		tsid_fd = bfsec->uf_sid;
+		inode = d_inode(path->dentry);
+
+		ad.type = LSM_AUDIT_DATA_PATH;
+		ad.u.path = *path;
+	} else {
+		struct file_security_struct *fsec = selinux_file(file);
+
+		tsid_fd = fsec->sid;
+		inode = file_inode(file);
+
+		ad.type = LSM_AUDIT_DATA_FILE;
+		ad.u.file = file;
+	}
+
+	if (ssid != tsid_fd) {
+		rc = avc_has_perm(ssid, tsid_fd, SECCLASS_FD, FD__USE, &ad);
 		if (rc)
-			goto out;
+			return rc;
 	}
 
 #ifdef CONFIG_BPF_SYSCALL
-	rc = bpf_fd_pass(file, cred_sid(cred));
+	/* regardless of backing vs user file, use the underlying file here */
+	rc = bpf_fd_pass(file, ssid);
 	if (rc)
 		return rc;
 #endif
 
 	/* av is zero if only checking access to the descriptor. */
-	rc = 0;
 	if (av)
-		rc = inode_has_perm(cred, inode, av, &ad);
+		return inode_has_perm(cred, inode, av, &ad);
 
-out:
-	return rc;
+	return 0;
+}
+
+/* Check whether a task can use an open file descriptor to
+   access an inode in a given way.  Check access to the
+   descriptor itself, and then use dentry_has_perm to
+   check a particular permission to the file.
+   Access to the descriptor is implicitly granted if it
+   has the same SID as the process.  If av is zero, then
+   access to the file is not checked, e.g. for cases
+   where only the descriptor is affected like seek. */
+static inline int file_has_perm(const struct cred *cred,
+				const struct file *file, u32 av)
+{
+	return __file_has_perm(cred, file, av, false);
 }
 
 /*
@@ -3799,6 +3822,17 @@ static int selinux_file_alloc_security(struct file *file)
 	return 0;
 }
 
+static int selinux_backing_file_alloc(struct file *backing_file,
+				      const struct file *user_file)
+{
+	struct backing_file_security_struct *bfsec;
+
+	bfsec = selinux_backing_file(backing_file);
+	bfsec->uf_sid = selinux_file(user_file)->sid;
+
+	return 0;
+}
+
 /*
  * Check whether a task has the ioctl permission and cmd
  * operation to an inode.
@@ -3916,42 +3950,55 @@ static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd,
 
 static int default_noexec __ro_after_init;
 
-static int file_map_prot_check(struct file *file, unsigned long prot, int shared)
+static int __file_map_prot_check(const struct cred *cred,
+				 const struct file *file, unsigned long prot,
+				 bool shared, bool bf_user_file)
 {
-	const struct cred *cred = current_cred();
-	u32 sid = cred_sid(cred);
-	int rc = 0;
+	struct inode *inode = NULL;
+	bool prot_exec = prot & PROT_EXEC;
+	bool prot_write = prot & PROT_WRITE;
+
+	if (file) {
+		if (bf_user_file)
+			inode = d_inode(backing_file_user_path(file)->dentry);
+		else
+			inode = file_inode(file);
+	}
+
+	if (default_noexec && prot_exec &&
+	    (!file || IS_PRIVATE(inode) || (!shared && prot_write))) {
+		int rc;
+		u32 sid = cred_sid(cred);
 
-	if (default_noexec &&
-	    (prot & PROT_EXEC) && (!file || IS_PRIVATE(file_inode(file)) ||
-				   (!shared && (prot & PROT_WRITE)))) {
 		/*
-		 * We are making executable an anonymous mapping or a
-		 * private file mapping that will also be writable.
-		 * This has an additional check.
+		 * We are making executable an anonymous mapping or a private
+		 * file mapping that will also be writable.
 		 */
-		rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
-				  PROCESS__EXECMEM, NULL);
+		rc = avc_has_perm(sid, sid, SECCLASS_PROCESS, PROCESS__EXECMEM,
+				  NULL);
 		if (rc)
-			goto error;
+			return rc;
 	}
 
 	if (file) {
-		/* read access is always possible with a mapping */
+		/* "read" always possible, "write" only if shared */
 		u32 av = FILE__READ;
-
-		/* write access only matters if the mapping is shared */
-		if (shared && (prot & PROT_WRITE))
+		if (shared && prot_write)
 			av |= FILE__WRITE;
-
-		if (prot & PROT_EXEC)
+		if (prot_exec)
 			av |= FILE__EXECUTE;
 
-		return file_has_perm(cred, file, av);
+		return __file_has_perm(cred, file, av, bf_user_file);
 	}
 
-error:
-	return rc;
+	return 0;
+}
+
+static inline int file_map_prot_check(const struct cred *cred,
+				      const struct file *file,
+				      unsigned long prot, bool shared)
+{
+	return __file_map_prot_check(cred, file, prot, shared, false);
 }
 
 static int selinux_mmap_addr(unsigned long addr)
@@ -3967,36 +4014,80 @@ static int selinux_mmap_addr(unsigned long addr)
 	return rc;
 }
 
-static int selinux_mmap_file(struct file *file,
-			     unsigned long reqprot __always_unused,
-			     unsigned long prot, unsigned long flags)
+static int selinux_mmap_file_common(const struct cred *cred, struct file *file,
+				    unsigned long prot, bool shared)
 {
-	struct common_audit_data ad;
-	int rc;
-
 	if (file) {
+		int rc;
+		struct common_audit_data ad;
+
 		ad.type = LSM_AUDIT_DATA_FILE;
 		ad.u.file = file;
-		rc = inode_has_perm(current_cred(), file_inode(file),
-				    FILE__MAP, &ad);
+		rc = inode_has_perm(cred, file_inode(file), FILE__MAP, &ad);
 		if (rc)
 			return rc;
 	}
 
-	return file_map_prot_check(file, prot,
-				   (flags & MAP_TYPE) == MAP_SHARED);
+	return file_map_prot_check(cred, file, prot, shared);
+}
+
+static int selinux_mmap_file(struct file *file,
+			     unsigned long reqprot __always_unused,
+			     unsigned long prot, unsigned long flags)
+{
+	return selinux_mmap_file_common(current_cred(), file, prot,
+					(flags & MAP_TYPE) == MAP_SHARED);
+}
+
+/**
+ * selinux_mmap_backing_file - Check mmap permissions on a backing file
+ * @vma: memory region
+ * @backing_file: stacked filesystem backing file
+ * @user_file: user visible file
+ *
+ * This is called after selinux_mmap_file() on stacked filesystems, and it
+ * is this function's responsibility to verify access to @backing_file and
+ * setup the SELinux state for possible later use in the mprotect() code path.
+ *
+ * By the time this function is called, mmap() access to @user_file has already
+ * been authorized and @vma->vm_file has been set to point to @backing_file.
+ *
+ * Return zero on success, negative values otherwise.
+ */
+static int selinux_mmap_backing_file(struct vm_area_struct *vma,
+				     struct file *backing_file,
+				     struct file *user_file __always_unused)
+{
+	unsigned long prot = 0;
+
+	/* translate vma->vm_flags perms into PROT perms */
+	if (vma->vm_flags & VM_READ)
+		prot |= PROT_READ;
+	if (vma->vm_flags & VM_WRITE)
+		prot |= PROT_WRITE;
+	if (vma->vm_flags & VM_EXEC)
+		prot |= PROT_EXEC;
+
+	return selinux_mmap_file_common(backing_file->f_cred, backing_file,
+					prot, vma->vm_flags & VM_SHARED);
 }
 
 static int selinux_file_mprotect(struct vm_area_struct *vma,
 				 unsigned long reqprot __always_unused,
 				 unsigned long prot)
 {
+	int rc;
 	const struct cred *cred = current_cred();
 	u32 sid = cred_sid(cred);
+	const struct file *file = vma->vm_file;
+	bool backing_file;
+	bool shared = vma->vm_flags & VM_SHARED;
+
+	/* check if we need to trigger the "backing files are awful" mode */
+	backing_file = file && (file->f_mode & FMODE_BACKING);
 
 	if (default_noexec &&
 	    (prot & PROT_EXEC) && !(vma->vm_flags & VM_EXEC)) {
-		int rc = 0;
 		/*
 		 * We don't use the vma_is_initial_heap() helper as it has
 		 * a history of problems and is currently broken on systems
@@ -4010,11 +4101,15 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
 		    vma->vm_end <= vma->vm_mm->brk) {
 			rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
 					  PROCESS__EXECHEAP, NULL);
-		} else if (!vma->vm_file && (vma_is_initial_stack(vma) ||
+			if (rc)
+				return rc;
+		} else if (!file && (vma_is_initial_stack(vma) ||
 			    vma_is_stack_for_current(vma))) {
 			rc = avc_has_perm(sid, sid, SECCLASS_PROCESS,
 					  PROCESS__EXECSTACK, NULL);
-		} else if (vma->vm_file && vma->anon_vma) {
+			if (rc)
+				return rc;
+		} else if (file && vma->anon_vma) {
 			/*
 			 * We are making executable a file mapping that has
 			 * had some COW done. Since pages might have been
@@ -4022,13 +4117,29 @@ static int selinux_file_mprotect(struct vm_area_struct *vma,
 			 * modified content.  This typically should only
 			 * occur for text relocations.
 			 */
-			rc = file_has_perm(cred, vma->vm_file, FILE__EXECMOD);
+			rc = __file_has_perm(cred, file, FILE__EXECMOD,
+					     backing_file);
+			if (rc)
+				return rc;
+			if (backing_file) {
+				rc = file_has_perm(file->f_cred, file,
+						   FILE__EXECMOD);
+				if (rc)
+					return rc;
+			}
 		}
+	}
+
+	rc = __file_map_prot_check(cred, file, prot, shared, backing_file);
+	if (rc)
+		return rc;
+	if (backing_file) {
+		rc = file_map_prot_check(file->f_cred, file, prot, shared);
 		if (rc)
 			return rc;
 	}
 
-	return file_map_prot_check(vma->vm_file, prot, vma->vm_flags&VM_SHARED);
+	return 0;
 }
 
 static int selinux_file_lock(struct file *file, unsigned int cmd)
@@ -7140,6 +7251,7 @@ struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {
 	.lbs_cred = sizeof(struct cred_security_struct),
 	.lbs_task = sizeof(struct task_security_struct),
 	.lbs_file = sizeof(struct file_security_struct),
+	.lbs_backing_file = sizeof(struct backing_file_security_struct),
 	.lbs_inode = sizeof(struct inode_security_struct),
 	.lbs_ipc = sizeof(struct ipc_security_struct),
 	.lbs_key = sizeof(struct key_security_struct),
@@ -7363,9 +7475,11 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 
 	LSM_HOOK_INIT(file_permission, selinux_file_permission),
 	LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),
+	LSM_HOOK_INIT(backing_file_alloc, selinux_backing_file_alloc),
 	LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),
 	LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat),
 	LSM_HOOK_INIT(mmap_file, selinux_mmap_file),
+	LSM_HOOK_INIT(mmap_backing_file, selinux_mmap_backing_file),
 	LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr),
 	LSM_HOOK_INIT(file_mprotect, selinux_file_mprotect),
 	LSM_HOOK_INIT(file_lock, selinux_file_lock),
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index 816fde5a5896..fcb46793898f 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -86,6 +86,10 @@ struct file_security_struct {
 	u32 pseqno; /* Policy seqno at the time of file open */
 };
 
+struct backing_file_security_struct {
+	u32 uf_sid; /* associated user file fsec->sid */
+};
+
 struct superblock_security_struct {
 	u32 sid; /* SID of file system superblock */
 	u32 def_sid; /* default SID for labeling */
@@ -190,6 +194,13 @@ static inline struct file_security_struct *selinux_file(const struct file *file)
 	return file->f_security + selinux_blob_sizes.lbs_file;
 }
 
+static inline struct backing_file_security_struct *
+selinux_backing_file(const struct file *backing_file)
+{
+	void *blob = backing_file_security(backing_file);
+	return blob + selinux_blob_sizes.lbs_backing_file;
+}
+
 static inline struct inode_security_struct *
 selinux_inode(const struct inode *inode)
 {